AcS43| 


FIRST  LINES 


OF 


PHYSIOLOGY.  /S'/^ 


BY 

ALBERT  VON  HALLER. 


TRANSLATED  FROM  THE 

THIRD  LATIN  EDITION. 


TO  WHICH  IS  ADDED, 

A TRANSLATION  OF  THE 

INDEX, 

COMPOSED  FOR  THE  EDINBURGH  EDITION, 
PRINTED  UNDER  THE  INSPECTION 
OF  DR.  WILLIAM  CULLEN. 


FIRST  AMERICAN  EDITION. 


TROY  ; 

PRINTED  BY  OBADIAH  PENNIMAN  & CO. 

SOLD  BY  THEM  AT  THEIR  STORE,  RIVER-STREET  ; BY  C.  R. 
& G.  WEBSTER,  AND  D.  & S.  WHITING,  ALBANY ; THO- 
MAS & ANDREWS, 'WEST  & GREENLEAF,  J.  WEST,  W.  P.  & 
L.  BLAKE,  C.  BINGHAM,  AND  MANNING  & LORING,  BOS- 
TON ; AND  P.  BYRNE,  PHILADELPHIA. 


1803. 


Digitized  by  the  Internet  Archive 
in  2016 


https://archive.org/details/firstlinesofphys02hall 


ADVERTISEMENT 


TO  THE  EDINBURGH  EDITION^ 


1 HE  correftlon  of  this  volume  for  the  prefs  was  un- 
iSertaken  at  the  defire  of  the  Publilhers.  Having  already  under- 
gone three  editions,  the  prelent  Editor  believed,  that  a careful 
perufal  of  the  proof-lheets,  and  attention  to  the  typographical 
accuracy  of  die  work,  would  chiefly  conllitute  his  fliare  in  the 
publication.  On  collating,  however,  the  laft  edition  with  the 
original  of  Haller,  it  appeared,  that  few  fentences,  and  fcarce- 
ly  one  paragraph,  conveyed  the  true  meaning  of  the  Author. 
In  many  places,  the  fenfe  was  totally  miftaken,  fometimes  per- 
verted, and  the  omiffions  and  interpolations  were  both  fo  nu- 
merous, and  lb  prejudicial  to  the  work,  that  thofe  who  have 
formed  their  opinion  of  the  value  of  Haller’s  Firfl;  Lines, 
from  any  tranflation  in  the  Englilh  language,  mull  have  form- 
ed an  opinion  of  them,  highly  detrimental  to  the  well  deferved 
reputation  of  the  Author.  In  die  prefent  edition,  with  much 
labour,  the  Editor  has  endeavoured  to  corredl  thefe  miftakes, 
to  fupply  what  was  omitted,  and  to  expunge  the  interpolations ; 
in  Ihort,  to  give  Haller’s  Firh  Lines  in  Englilh. 

The  very  great  deviations  made  by  the  original  Tranllator 
from  the  meaning  of  the  Author,  have  betrayed  the  prefent 
Editor  into  an  oppolite  fault,  that  of  making  his  edition  more 
literal  than  perhaps  is  confillent  with  the  true  idiom  of  die 
Englilh  language.  For  this  imperfection  he  has  no  other  apol- 
ogy to  offer  : but  for  the  omilTion  of  Dr.  Wrisberg’s  Notes, 
one  is  neceflary.  Of  thefe  notes,  many  are  excellent ; but  as 
moft  of  them  are  literary,  fome  controverfial,  and  others  but 
add  a new  conjedlure  upon  points  not  yet  underftood,  and,  final- 
ly, as  they  do  not  now  fulfil  their  original  Intention  of  fupply- 
ing  every  difcovery  made  in  Phyfiology  fince  Haller’s  time, 
it  was  thought  proper  not  to  increafe  the  fize  and  price  of  the 
volume  by  their  infertion. 


CONTENTS. 


CONTENTS. 


ChAp.  Pace. 

l.  Of  fibre  and  cellular  fubftance, i 

II.  Of  the  veflhls, ii 

m.  Of  the  motion  of  the  blood  tlirough  the  veins  and 

arteries,  or  circulation, 26 

IV.  Of  the  hearty  32 

V.  Of  the  nature  of  tlie  blood  and  humours  of  the 

human  body, 60 

VI.  Of  the  common  oifices  of  arteries, 69 

VII.  Of  fecretion, 85 

VIII.  Of  refpiration, 104 

IX.  Of  voice  and  fpeech, ; . 132 

X.  Of  the  brain  and  nerves, . 142 

XI.  Of  mufcular  motion, 186 

XII.  Of  the  fenfe  of  touch, 201 

XIII.  Oftafie, 215 

XIV.  Offinell, 22  r 

XV.  Of  hearing,  227 

XVI.  Of  fight, 242 

XVII.  Of  the  internal  fenfes, 269 

XVIII.  Of  maflication,  faliva,  and  deglutition,  . . 288 

XIX.  Of  the  aftion  of  the  ftomach  on  the  food,  . . 305 

XX.  Of  the  omentum,  . . 321 

XXL  Of  the  fpleen,  . . 329 

XXII.  Of  the  pancreas,  334 

XXIII.  Of  the  liver,  gall  bladder,  and  bile,  . . . 336 

XXIV.  Of  the  linall  inteftines, 354 

XXV.  Of  the  large  inteftines, 365 

XXV. *  Of  the  chyliferous  velTels, 374 

XXVI.  Of  the  kidneys^,  bladder,  and  urine,  . . . 380 

XXVII.  Of  the  male  organs  of  generation,  . . . 395 

XXVIII.  Of  the  virgin  uterus, 412 

XXIX.  Of  conception, 424 

XXX.  Of  nutrition,  growth,  life  and  death,  . . . 462 


FIRST 


f 


FIRST  LINES 


OF 

PHYSIOLOGY, 


CHAP.  I. 


FIBRE. CELLULAR  SUBSTANCE. 

1.  ^ I 'HE  moft  fimple  parts  of  the  human  body, 
§ are  either  fluid  or  folid.  As  the  fluids 
are  of  different  kinds,  we  fhall  conflder  each  of 
them  in  its  proper  place ; and  premife  the  hiffory 
of  the  folids,  which  are  moft  fimple,  and  the  true 
bafis  of  the  body,  to  the  confideration  of  the  other 
parts. 

II.  The  folid  parts  of  animals  and  vegetables 
have  this  fabric  in  common  ; that  their  elements, 
as  feen  by  the  moft  powerful  microfcopes,  are  ei- 
ther fibres,  or  laminae,  or  unorganized  gluten. 

III.  Fibres  for  the  moft  part,  refernble  lines  of 
very  minute  breadth,  or  rather  flender  cylinders. 
Their  moft  permianent  particles  are  demonftrated  to 

B be 


/ 6 3ii / 


FIBRE 


Chap.  I. 


be  earthy,  by  combuftion,  or  long  continued  pu- 
trefaclion. 

IV.  Thefe  earthy  particles  derive  conneclion  and 
the  power  of  coheiion,  not  from  themfelvcs,  but 
from  interpofed  gluten.  We  know  this  from  the 
preceding  obfervations,  (iii.)  and  the  eafy  experi- 
ment, in  which  a burnt  hair,  whofe  parts  hang  fthl 
together,  recovers  a certain  degree  of  firmnefs  by 
being  dipped  in  water  or  oil.  Ivory  and  bones  alfo 
become  friable,  by  the  extraction  of  their  gelly. 
Long  expofure  to  weather  elFecls  a hmilar  change, 
rendering  bones  a true  earth,  abforbent  and  bibu- 
lous. But  even  bone,  become  friable  from  having 
its  gelly  extracted,  reacquires  its  olleous  hardr.efs, 
when  that  geily  is  reftored.  I’he  more  fimple  an- 
imals conllft  entirely  of  this  gluten. 

v.  Laitly,  the  chemical  analyhs  of  bone,  and  hair, 
the  geily  of  bone,  ivory,  and  horn,  the  nature  of 
our  aliments,  &c.  prove,  that  this  gluten  is  com- 
poied  of  water,  incorporated  with  oil  by  animal  life, 
blor  does  any  other  kind  of  gluten  unite  the  parts 
of  animals  more  ilrongly,  as  we  fee  in  hze  and 
comm.on  glue. 

VI.  The  primary  fimiple  fibre,  fuch  as  we  rather 
comprehend  from  reafon  than  fenfe,  is  compofed  of 
earthy  particles,  adhering  longitudinally,  and  con- 
nefled  by  intervening  and  cohefive  gluten. 

VII.  But  the  fibres  v hich  appear  primary  to  the 
fight,  are  of  two  kinds.  The  lirft  is  linear,  wliole 
length  is  coniiderable  in  proportion  to  its  breadth, 
.and  whofe  elementary  particles  lie  in  a flraight  line, 
and  thus  generally  parallel  to  thofe  contiguous. 
W e fee  examples  of  this  kind  of  fibre  in  bone, 
mofl  eafily  in  thofe  of  the  fetus,  and  alfo  in  ten- 
dons, ligaments  and  mufcles,  always  recoilefblng 
that  the  eye  fees  not  the  m.cfi;  minute  fibres,  but 
only  the  larger  ones  compofed  of  tliefe,  and  fimi- 
lar  to  them  in  flraiglitnefs  and  flcndernefs.  That 

the 


Chap.  I.  CELLULAR  SUBSTANCE. 


3 

the  ultimate  fibres  are  perfectly  fimilar,  we  are 
convinced  by  the  microfcopes  of  Muys  and  Lecu- 
wenhoeck,  in  which  the  mufcular  fibres,  even  the 
molt  minute,  appear  exactly  like  the  larger  ones, 
and  perfectly  linear. 

VIII.  The  fecond  kind  confifts  of  laminae,  in 
which,  a breadth  often  greater,  is  conjoined  with  a 
Ihorter  length.  A loole  web  of  thefe  has  got  the 
name  of  Cellular  Tunic,  though  the  term  Tunic  is 
on  many  accounts  improper. 

IX.  This  cellular  fubftance  is  compofed  of  an  in- 
finite number  of  fmall  laminae,  which,  by  their 
various  dire<5tions,  inclofe  fmall  fpaces  and  cavities, 
and  join  all  the  parts  of  the  human  body,  afford- 
ing an  extenfive  and  firm  union,  with  fufficient 
mobility.  But  in  this  web  there  is  the  greatefi;  di- 
verfity  in  the  proportion  of  the  folids  to  the  cavi- 
ties; in  the  breadth  and  firmnefs  of  the  laminae;  in 
the  nature  of  the-  contained  liquor,  which  is  either 
more  watery  or  more  oily ; and  in  the  admixture 
of  fibres  and  filaments,  of  which  there  is  a great 
quantity  in  fome  places,  as  in  the  coats  of  the  ar- 
teries, in  others  almofi;  none,  as  under  the  fkin. 

x.  Of  this  cellular  fubilance  when  compacted, 
from  the  laminse  concreting,  and  being  compreffed 
by  the  a<5iion  of  the  incumbent  mufcles,  diftend- 
ing  liquid,  or  other  caufe,  broad  plates  are  formed, 
which  are  either  rectilineal  in  general,  and  more 
properly  called  Membranes ; or  convoluted  into 
cylinders  and  cones,  vcith  liquids  flowing  through 
their  cavities,  and  denominated  Veffels  ; or  extend- 
ing round  fome  place  in  a plane  parallel  to  it,  get 
the  name  of  Tunics.  That  tunics  are  formed  of 
cellular  fubftance,  is  proved  in  the  aorta,  fkin,  pe- 
ricardium, and  dura  mater,  by  ocular  infpection, 
and  efpecially  by  maceration.  The  coats  of  the 
mufcles,  are  alfo  evidently  cellular,  and  fimilar  to 
other  tunics.  The  fame  thing  is  alfo  proved  from 
the  eafy  change  of  the  dartQS,  and  the  nervous 
II  2 meinbrane 


4 


FIBRE. 


CllAP.  I. 


membrane  of  the  intelHnes,  into  cellular  fubftance, 
l>y  inhation  ; and  from  the  hard  and  thick  mem- 
branes formed  in  enc)dled  tumors,  which  are  mere 
productions  of  cellular  texture.  In  the  integu- 
ments, being  very  clofely  compacted  in  continued 
n;radation,  it  forms  the  true  fkin  lyinG:  under  the 
epidermis  j and  being  thence  continued,  it  is  at 
laft  partly  refolved  into  the  fubcutaneous  cellular 
texture  fiUed  with  fat. 

XI.  The  veffels  which  colour  the  tunics  are  an 
addition  to  tlie  cellular  fubftance,  and  in  no  wile 
cll'ential  to  the  nature  of  membrane,  but  fupcr- 
addcd  to  the  membrane  formed  of  the  cellular 
fubhance.  Betvceen  the  meihes  of  the  intefdnal 
netv/ork  of  veffels,  when  moll  perfectly  fiUed  by 
the  Ruyfcliian  art,  white  cellular  fubffance  re- 
mains, e\'en  then  greatly  exceeding  the  bulk  of 
the  veffels,  although  being  preternaturally  diitend- 
ed,  they  occupy  a.  greater  fpace.  But  I do  not 
knov/  any  membranes  compofed  of  fibres  mterv/o- 
ven  with,  and  decuflating  each  other  ; unlefs  you 
conhder  as  fach  the  ligamentary  or  tendinous  hbres 
which  are  fpread  over  true  membranes. 

XII.  Cellular  fubffance  is  found  in  the  human 
body,  wdierever  there  is  a v^efl'cl  or  mufcular  fibre, 
without  exception,  as  far  as  I know. 

XIII.  The  other  elementary  fubftance  of  the 
human  body,  (ii.)  which  cannot  be  truly  called 
cither  a fibre  or  cellular  lamince,  is  a mere  extra- 
vafited  gluten,  concreted,  not  into  fibres,  but  in 
the  fnaces  betwixt  them.  This  is  manifeft  in  the 

A 

bones,  whofe  fibres  are  feen  v^ery  diftincHy  in  tlie 
foetus,  with  veffels  running  in  the  intervals  be- 
i W'cen  them  ; fo  that  the  fkull  in  every  part,  re- 
fcmbles  a comb.  This  fabric  is  fo  altered  in  the 
adult,  that  tlie  intervals  being  filled  up  by  fluid, 
cxtras'afcitcd  in  the  fnaces  betveixt  the  fibres,  as 
liappens  with  the  juice  of  madder,  and  the  edges 

being 


Chap.  I.  CELLULAR  SUBST.\I>TCE. 


5 

being  agglutinated,  laminoe  are  formed.  The  car- 
tilages feem  to  be  fcarcely  any  thing  elfe  than  con- 
creted gluten. 

XIV.  But  here  the  order  of  nature  fcems  to  be, 
that  the  fibres  above  mentioned  (in.)  are  all  ori- 
ginally formed  of  this  gluten.  That  the  cellu- 
lar fubftance  (vii.)  is  thus  formed,  appears  from 
thofe  cellular  fibres,  produced  in  the  thorax  from 
concreted  vapour,  which  joins  the  furface  of  the 
lungs  to  the  pleura,  and  perfectly  refembling  the  * 
true  and  natural  cellular  fubftance,  even  though 
compacted  of  infpiflated  pus.  The  fame  appears 
alfo  from  a comparifon  of  the  foetus  with  the 
adult ; for,  inftead  of  the  abundant  fubcutaneous 
cellular  fubftance,  the  foetus  has  a mere  jelly  inter- 
pofed  betwixt  the  fkin  and  mufcles,  which  have 
already  acquired  greater  firmnefs  ; from  the  mor- 
bid diflblution  of  the  membranes  of  the  mufcles 
into  a mere  gluten  ; and  from  a fimilar  change 
into  glue  of  the  fkin,  tendons,  and  ligaments  of 
animals,  by  means  of  boiling  water.  Clots  of 
coagulated  blood  ; the  fanguineous  membranes  of 
Ruyfch  ; Albinus’s  membranes  formed  of  mucus, 
polypus,  filk  and  glue,  alfo  illuftrate  this  theory. 
Laftly,that  the  bony  fibres  themfelves  are  formed  of 
compacted  gluten,  is  fhown  from  difeafes  in  which 
the  hardeft  bones,  by  a liquefaction  of  their  gluten , 
return  into  cartilage,  flefli,  and  jelly.  Similar 
changes  are  made  on  the  bones  of  fifties  and  other 
fdbftances  by  Papin’s  digefter. 

XV.  It  feems,  then,  that  an  albuminous  fiui'l, 
with  a fmaU  portion  of  earth,  faTi  concretes  in- 
to filam.ents,  from  fome  preflure,  whofe  caufes  we 
now  pafs  over.  Thefe  by  the  mutual  attraction 
of  cohefion,  leaving,  however,  fpaces  between 
them,  compofe  the  cellular  texture,  after  hav- 
ing acquired  fomc  firmnefs  from  the  clofenefs  of 
the  earthy  rarticics,  which  follows  the  expul- 


6 


FIBRE. 


Chap.  E 


lion  of  the  too  aqueous  gluten.  This  fubftance, 
wherever  its  laminae  are  lubjected  to  greater  prcf- 
fure,  turns  into  fibres  and  tunics ; and,  laftly,  with 
unorganized  gluten  (xiv.)  concretes  into  bone, 
(xv.)  Hence,  in  general,  all  parts  of  the  body, 
from  the  foftefi;  to  the  hardeft,  feem  to  differ  on- 
ly in  the  latter  having  more  of  the  earthy  par- 
ticles, and  thefe  more  clofely  compacted,  with  lefs 
aqueous  gluten  ; vchile  in  the  foft  parts  there  is 
lefs  earth  and  more  gluten. 

XVI.  The  cellular  texture  is  made  up  of  fibres 
and  laminae  (viii.)  which  are  neither  hollow  nor 
vafcular,  although  it  is  coloured  by  acceffor^"  vef- 
fels,  but  folid.  The  following  are  its  chief  va- 
rieties. In  fome  parts  it  is  loofe,  and  formed 
of  long  and  diftant  liminas  ; in  others  thin,  and 
compofed  of  llrort  fibres.  I find  it  fherteft  be- 
twixt the  fclerotica  and  choroides  of  the  eye, 
efpeciaHy  of  animals,  and  betwixt  the  arachnoides 
and  pia  mater  of  the  brain.  I alfo  find  it  tender, 
but  more  confpicuous,  betwixt  every  two  coats  of 
the  intefiines,  fiomach,  bladder,  and  ureters  ; in 
the  veficles  of  the  lungs,  under  the  pulp  of  the 
glans  penis  ; and  between  the  ftnall  kernels  of  the 
vifeera  and  glands.  It  is  compofed  of  ftill  longer 
fibres,  where  it  accompanies  the  veffels,  under  the 
name  cf  Vagina,  through  the  vifeera,  and  particu- 
larly the  liver  and  lungs  ; and  is  vaftly  firmer  in 
the  veffels  which  go  to  the  head  and  limbs.  Its 
principal  ufe  is  to  bind  together  the  contiguous 
membranes,  vclfcls,  and  fibres,  in  fuch  a manner  as 
to  allow  them  a due  des;ree  of  motion.  But  the 
cellular  fubftance,  as  hitherto  deferibed,  hardly 
ever  contains  any  fat  ; but  is  moiftened  by  a w^a- 
tery,  gelatinous  and  fomewhat  oily  vapour,  exhaled 
from  the  arteries,  and  received  again  into  the 
veins.  The  truth  of  this  is  eafily  dcmonftrable 
from  injections  of  water,  ifinglafs  or  oil,  made  in 
ah  parts  of  the  body.  When  this  vapour  is  want- 


Chap.  I.  CELLULAR  SUBSTANCE. 


7 

ing,  the  filaments  cohere,  and  the  contiguous 
membranes  are  united,  with  lofs  of  motion. 

XVII.  The  cellular  texture  is  more  lax,  and  form- 
ed of  laminx  rather  than  fibres,  where  it  divides 
the  mufcular  fibres,  even  the  moft  minute  ; wLere 
it  loofely  accompanies  and  fuftains  the  veffels  ; and 
within  the  cavities  of  the  bones,  where  it  is  com- 
pofed  of  bony  as  w'ell  as  membranous  laminae. 
That  is  likewife  very  lax,  which,  under  the  fur- 
face  of  the  body,  is  every  where  interpofed  be- 
twixt the  mufcles  and  the  Ikin  ; but  theiaxeft  of 
all  is  that  which  furrounds  with  very  wide  cells 
the  genital  parts  of  the  male. 

XVIII.  Into  the  empty  meflies  of  this  cellular 
texture  (xvii.)  there  is  poured  almofi;  every  where, 
in  the  foetus,  firft  a gelly,  then  a grumous,  and  laft- 
ly,  under  the  whole  Ikin,  and  in  its  pits,  a clotted 
fat.  This  fubftance  is  lighter  than  water,  infipid, 
inflammable,  becomes  folid  in  the  cold,  is  found 
in  greater  quantity  about  the  kidneys  and  in  gra- 
minivorous animals  ; in  fillies,  v/hile  alive,  and 
probably  alfo  in  man,  nearly  fluid,  though  apt  to 
coagulate.  In  it  an  acid  fait,  almofl  in  the  pro- 
portion of  one-fixth,  is  united  with  oil. 

XIX.  Through  this  cellular  texture  the  blood- 
veffels  run  and  are  divided  ; from  the  arterial  ex- 
tremities of  which,  the  fat  is  depofited  and  a^- 
forbed  by  the  venous.  The  paflage,  from  the  ar- 
teries into  the  adipofe  cells,  is  fo  immediate  and 
free;  that  they  mull  open  by  very  large  mouths, 
fmee  they  admit  injeffed  mercury,  air,  water,  fize, 
and  oil,  which  is  always  very  fluggilh,  even  in  liv- 
ing animals.  It  is  not  fecreted  by  any  long  duels 
of  particular  fabric,  but  tranfudes  on  all  • fides 
through  the  whole  extent  of  the  artery  ; infomuch 
that,  when  an  artery  is  filled  with  water,  there  is  no 
part  of  the  furrounding  cellular  fubftance  which  is 
not  moiflened.  The  warm  fat,  during  the  pulfation 
of  i^je  arteries,  eaiily  finds  out  the  iarne  paffages. 

How 


8 


FIBRE. 


Chap.  I. 


Hov/  ^ickly  it  is  collected,  appears  from  the 
ipeedy  renovation  of  fatnefs  after  acute  difeafes. 

XX.  But  that  this  fat  is  abforbed  by  the  veins, 
we  are  taught  from  the  fudden  effects  which  muf- 
cular  exercife  has  in  confuming  the  fat,  more  ef- 
pecially  of  animals  in  which  it  abounds  ; alfo 
from  its  confumption  in  fevers  ; from  the  cure  of 
droplies,  v/here  the  water  effufed  into  the  ceUu- 
lar  fubftance  is  in  a manner  abforbed  and  thrown 
out  by  the  inteftinal  tube  ; and,  lafdy,  from  the 
venous  tranfudation  of  water  and  oil,  when  inject- 
ed by  the  fyringe,  obferved  in  every  part  of  the 
body.  Are  nerves  diftributed  upon  the  adipofe 
cells  ? It  is  certain  they  run  through  this  fub- 
fcance,  and  every  where  divide  in  it,  into  the  mi- 
nuteft  filaments,  fo  that  they  can  no  longer  be 
traced  by  the  knife.  That  they  terminate  in  it,  is 
not  probable  j for  the  fat  is  both  infenfible  and 
unirritable. 

XXI.  The  rneflies  betwdxt  the  laminae  of  the 
cellular"  membrane,  are  every  where  open,  and 
unite  in  forming  one  continuous  cavity  through- 
out the  whole  body.  This  appears  from  the  infla- 
tion of  the  &in  over  all  the  body,  which  butchers, 
and  likevvile  the  furgeons  of  Ethiopia,  efTecl;  by  a 
finglc  wound  ; from  ernphyfema,  in  wdiich  the  air 
received  by  a wound  of  the  fldn,  being  retained, 
caufes  a fwellin?:  throughout  the  whole  bodv  ; 
from  the  paffage  of  bodies,  put  under  the  Ikin,  to 
a place  remote  from  that  at  which  they  entered  ; 
from  the  paffage  of  pus,  from  an  inflamed  place 
10  remote  ulcers  ; and,  finally,  from  difeafes,  in 
v/hich  water  depofited  in  ail  the  cellular  fub- 
ftance of  the  body,  is  comipletely  evacuated  by 
a fingle  incifion.  That  none  of  the  cellular  tex- 
ture is  excepted,  appears  from  a cafe  of  emphy- 
fema  in  v/hich  the  vitreous  body  of  tlie  eye  itfclf 
was  inflated  ; and  from  a difeafe,  in  which  the 

gelatinous 


Chap.  I.  CELLULAR  SUBSTxlNCE.  'g 

gelatinous  ferum  of  a dropfy  was  transfufed  even, 
into  the  cavernous  homes  or  the  penis. 

XXII.  The  great  importance  of  this  cellular 
flibftance  will  be  evident  to  all  who  confider,  that 
from  it  alone  proceeds  the  due  firmnefs  and  fta- 
bility  of  all  the  arteries,  nerves,  and  mufcular 
fibres,  and  confequently  of  all  the  ileili  and  vifcera 
formed  of  thefe  ; but  even  the  figures  of  the  parts, 
their  juft  length,  cavities,  curvatures,  flexures, 
depend  entirely  on  the  cellular  membrane,  being 
in  fome  places  of  a laxer,  and  in  others  of  a denfer 
fabric  : for  when  divided,  every  part  is  lengthened 
and  collapfes.  Of  this  fubftance,  with  veftels, 
nerves,  mufcular  and  tendinous  fibres,  (a  great 
part  of  which  are  however  formed  of  it,)  all  the 
vifcera,  all  the  mufcles,  glands,  ligaments  and  cap- 
fules,  are  compofed ; on  it  alone,  and  its  different 
length,  tenfion,  quantity  or  proportion,  the  diver- 
fity  of  our  glands  and  vifcera  depends  ; and,  laft- 
ly,  it  certainly  conftitutes  by  far  the  greateft  part 
of  the  body  itfelf,  if  indeed  the  whole  be  not 
formed  of  cellular  filaments  of  this  kind. 

XXIII.  It  poffeffes  a contracUIc  power,  different 
from  irritability,  which,  thougli  not  demonftrable 
by  experiments,  difpofes  the  cellular  fibre  to  ftiort- 
en  itfelf,  though  for  the  moft  part  flowly,  after 
having  been  ftretched.  This  power,  eycited  by 
cold,  renders  the  fldn  rigid  ; raifes  the  hairs  ; 
draws  up  tlie  ferotum  ; and,  after  geftation,  rc- 
ftores  the  Ikin  of  the  abdomen,  and  the  uterus,  to 
their  former  fize.  The  fame  force,  by  a gentle 
but  continual  contraftion,  promotes  the  fecretion 
of  fat  of  the  liquors  of  the  fubcutaneous  and  oth- 
er glands,  and  of  pus  : in  the  veins  and  recepta- 
cles, it  refifts  dilatation  ; and,  when  that  is  taken 
off,  it  regains  its  former  fiiortnefs.  In  tlie  foetus, 
this  gentle  force  is  among  the  principal  caufes  of 
the  changes  that  liappen  to  the  body. 


FIBRE. 


Chap.  I. 


to 

XXIV.  The  ufes  of  the  fat  are  various  ; it  every- 
where facilitates  the  motions  of  the  mufcles,  Icf- 
fens  their  attrition,  and  prevents  rigidity  : it  fils 
up  the  fpaces  between  the  mufcles,  and  the  cavi- 
ties about  many  of  the  vifeera,  in  fuch  a manner, 
that  it  readily  yields  to  their  motions,  and  yet 
fupports  them  when  at  reft  : it  principally  confti- 
tutes  the  weight  of  the  body  ; conducts  and  de- 
fends the  veflels  ; it  uniformly  diftends  the  fkin  ; 
ferves  as  a cuftiion  to  the  body,  and  renders  the 
whole  comely : it  probably,  by  mbdng  with  fome 
humours,  abates  their  acrimony  : it  has  a princi- 
pal fliare  in  forming  the  bile ; and,  by  tranluding 
through  the  cartilaginous  incruftations  of  the 
bones,  it  mixes  with  the  articular  liquid,  and  by 
abforption,  it  lubricates  their  fibres  : by  exhaling 
through  the  pores  of  the  Ikin,  it  refifts  the  dr)  ing 
fharpnefs  of  the  air  ; alfo,  by  exhaling  in  a living 
perfon  from  the  mefentery,  mefocolon,  omentum, 
and  round  the  kidneys,  it  lubricates  the  furfaces 
of  the  vifeera  with  a bland  vapour  ; and,  by  being 
interpofed,  prevents  their  concretion. 

XXV.  The  fat  is  depofited  into  the  cells  during 
lleep,  reft  of  body  and  mind,  and  dimaniflied  force 
of  circulation.  When  collected  in  too  great  a quan- 
tity, it  proves  injurious ; by  comprefling  the  veins  ; 
and,  impeding  the  action  of  the  heart,  it  produces 
afthma,  apoplexy  and  dropfy.  The  fame  humour 
is  taken  up  by  the  veins ; and,  being  more  rapidly 
moved  along  the  arteries,  by  violent  exercife,  ve- 
nery,  watchings,  cares  of  the  mind,  falhation, 
diarrhoea,  fever,  falling,  it  is  carried  beyond  the 
excretory  pores  : it  is  confumed  by  fuppuration. 
When  reftored  to  the  blood,  it  increafes  acute 
difeafes,  tinges  the  urine,  and  forms  a part  of  its 
fediment.  After  being  fuddenly  confumed,  it  is 
foon  renewed  again  from  healthy  humours  : but, 
in  a languid  habit,  a gelly,  inllead  of  fat,  is  depo- 
fited  into  the  cells,  caufing  auafiirca,  and  external 
hydrocele. 


Chap.  II. 


VESSELS. 


It 


; C K A P.  II. 

VESSELS. 

XXVI.  ^'1  ‘'HE  membranes  will  be  better  defcribed 
fingly.  There  are  many  things  common 
to  the  arteries.  They  are  long  extended  cones,  de- 
crealing  according  to  the  number  of  their  branches. 
But  where  arteries  run  for  fome  length,  without 
fending  off  large  branches,  their  convergency  is 
not  very  evident,  if  any ; and  at  length,  where 
they  are  called  capillaries,  and  wherever  they  give 
palTage  to  a lingle  globule,  they  are  either  cylin- 
drical, or  diminifli  very  imperceptibly ; their  tranf- 
verfe  fecUons  are  every  Vv^here  and  without  excep- 
tion circular,  when  the  artery  is  full.  Where  they 
fend  off  large  branches,  the  caliber  is  fuddeniy 
diminiflied,  infomuch  that  they  may  be  reckoned  a 
chain  of  cylinders,  of  which  every  one  is  narrower 
than  the  preceding.  If  you  reckon  them  cones, 
then  the  balls  of  the  cone,  common  to  all  the  arteries 
is  in  one  or  other  of  the  ventricles  of  the  heart ; 
and  the  apex  of  the  cone,  either  in  the  beginning 
of  a vein,  or  in  the  beginning  of  the  cylindrical 
part  of  the  artery,  or  unlefs  it  is  cylindrical,  in  an 
exhaling  veffel.  In  fome  places  they  feem  to  di- 
late ; at  leaft  they  certainly  become  wider,  after 
they  have  been  filled  and  difcended  with  wax ; 
poffibly  from  fome  obftruflion  which  caufes  the  in- 
jected vrax  to  diftend  that  part  of  the  artery  more 
than  the  reft.  Examples  of  this  kind  we  have  in 
the  vertebral  artery,  at  the  bafts  of  the  fkull ; in  the 
fplenic  ; in  the  flexure  of  the  carotid,  according  to 
Mr.  Cowper’s  injeClions  ; and,  laftiy,  unlefs  1 be 
much  deceived,  in  the  fpermatic  arteries.  In  all 
places,  iikewife,  where  the  ramifications  begin,  the 
diameter  of  the  artery  is  a little  increafed. 


XXVII. 


si 


VESSELS. 


Chap.  IL 


XXVII.  There  is  no  external  coat  proper  and 
common  to  all  arteries.  Tliey  derive  an  exter- 
nal and  merely  incum.bentintegument,inthe  thorax 
from  the  pleura,  and  in  the  abdomen  from  the  pe- 
ritonxum.  In  the  neck,  arm,  and  thigh,  a fort  of 
thicker  cellular  fubftance  furrounds  the  arteries. 
The  membrane  of  the  pericardium,  v.hich  on  all 
itdes  encircles  the  aorta,  returns  back  with  the 
veifels  to  the  heart.  The  dura  mater  imparts  a 
capfule  to  the  carotid,  as  it  paiies  out  of  the  ikull. 
But  the  fiiTt  true  membrane  of  the  arterial  tube,  is 
every  where  cellular,  and  fometimes  adipofe  as  in 
the  thorax. 

XXVIII.  Tlie  external  furface  of  this  cellular  coat 
is  of  a ioofer  texture,  coloured  by  a great  many 
fmall  veins  andarteries,and  permeated  by  nervesnot 
very  minute.  It  is  fometimes  fo  abundant,  that  its 
external  layers  feem  hardly  to  belong  to  the  arte- 
ry, but  appear  like  an  extraneous  texture  added  to 
it.  It  is  of  this  appearance  in  the  neck,  and  round 
the  inguinal,  fubciavian,  mefenteric,  coeliac,  and 
hepatic  arteries,  being  chiefly  compofed  of  long 
iilaments.  Thefe  are  the  Vaginx  of  the  Arteries,  of 
iome  eminent  men. 

XXIX.  As  this  cellular  coat  advances  more  inward- 
ly, and  nearer  to  the  cavity  of  the  artery,  it  becomes 
more  denie,  folia,  and  flbrous,  and  may  be  called  a 
proper  coat  of  the  artery.  That  there  is  no  tendi- 
nous coat  of  the  arteries  dlfcincf  from  tliis  cellular 
fubflancc,  is  evident  from  maceration,  by  which  tiic 
inmofl;  ftratum  of  this  arterial  tunic  becomes  cel- 
lular. 

XXX,  Within  the  former,  and  nearer  the  cavity 
of  the  artery,  we  And  libres,in  general  orbicular ; re- 
coliecfing,  however,  that  no  flbre  anywhere  makes 
a complete  circle  ; but  that  many  of  them  conjoin- 
ed, v/ith  their  extremities  turned  ofl 'fldeways,  feem 
to  form  one  ring.  Tliefe  fibres,  in  the  larger 
tranks,%-m  many  fliu.ta.fufliciently  apparent  from 

thciv 


Chap.  IL 


VESSELS. 


their  reddifli  colour  and  folidity  *,  but  in  tlie  fmall- 
er  arteries  they  are  by  degrees  more  diflicult  to 
demonftrate,  and  feem  to  be  wanting  in  the  arteries 
of  fmall  animals.  I have  never  obferved  them 
longitudinal.  Under  this  membrane,  but  more 
diflicult  to  demonftrate,  is  an  exceedingly  ftiort 
cellular  texture,  into  which  the  tophaceous  matter 
is  poured  when  an  artery  offifies. 

XXXI.  The  innermoft  coat  of  the  artery  is 
thin,  and  finely  poliftied  by  the  current  of  blood  ; 
it  covers  with  an  uninterrupted  lining  the  flefiiy 
fibres,  which  are  not  fufficiently  continuous,  and 
prevents  the  blood  from  infinuating  itfelf  into 
the  intervals.  It  is  every  where  fmooth  and  with- 
out valves ; although,  from  a fort  of  mechanical 
necefiity,  fometimes  certain  folds,  railed  into  a fe- 
mi circle  at  the  origin  of  branches,  project,  as  we 
fee,  at  the  branches  fent  off  from  the  arch  of  the 
aorta.  Yet,  in  arteries  of  the  vifcera,  the  inner- 
moft coat  is  fofter,  lax,  wrinkled,  and  almoft  fri- 
able, efpecially  in  the  ductus  arteriofus. 

xxxii.  The  arteries  themfelves  have  arteries, 
particularly  in  their  external  cellular  coat,  fpring- 
ing  on  all  fides  from  the  adjacent  fmall  arteries, 
num.erous,  branchy,  reticular,  all  very  minute,  even 
in  the  fmtus,  without  injection,  very  numerous. 
Nerves  every  where  delcend,  for  a great  way  along 
hhe  farface  of  the  arteries,  and  vanifih  in  the  cellu- 
lar fubftance  ; of  which  we  have  examples  in  the 
external  and  internal  carotids,  and  arch  of  the 
aorta.  From  thefe,  do  not  the  arteries  derive  a 
contractile  fpaftic  force,  different  from  fimple  elaf- 
ticity  ? Do  not  fevers,  faintings,  palfy  with  atro- 
phy, and  the  paffions  of  the  mind,  prove  fomething 
like  this  ? But  arteries  are  infenfible  and  unirrita- 
ble  ; and  if  they  are  conftricted  by  poifons,  they 
have  that  property  in  common  with  the  dead  fkin. 

xxxni.  The  fections  of  arteries  are  circular,  be- 
eaufe  they  are  elaftic  j this  is  the  reafon  why,  even 

from 


*4 


VESSELS. 


Chap.  If. 


fi'om  the  fmaU  arteries  of  the  teeth,  haemorrhages 
are  fometimes  fatal.  The  aorta,  indeed,  in  the 
thorax  and  abdomen,  the  carotids  in  the  neck,  and 
fome  other  arteries  of  the  dead  body,  when  not 
diftended,  appear  flat ; but  their  round  figure, 
and  circular  feedion,  are  always  reftored  by  injec- 
tion. By  their  elafticity,  arteries  fiirongly  com- 
prefs  the  finger  that  dilates  them,  and  more  tight- 
ly in  the  dea.d  than  in  the  living  body.  In  the 
living  body,  indeed,  it  yields  to  the  action  of  the 
heart ; but  vrhen  the  heart  is  relaxed,  inftantly 
contracts,  and  regains  its  former  diamieter ; this 
conflitutes  the  pulfe,  whofe  full  explication  will 
properly  follov'-  the  hiftory  of  the  heart ; at  pre- 
ient,  it  is  fufiicient  to  fay,  that  all  arteries  pulfate, 
although  the  fyftole  and  diaftole  can  be  perceived 
by  the  finger,  only  in  the  larger,  not  in  the  fmaller 
ones  ; and  though  in  the  ultimate  inflections  of  the 
arteries,  it  almoft  vanifhes  ; for,  by  an  increafed 
motion  of  the  blood,  even  the  fmaller  arteries  beat 
violently,  as  we  fee  in  inflammations.  They  con- 
tract lengthvdfc  ftrongly,  and  are  rendered  ihorter 
when  cut  entirely  acrofs. 

XXXIV.  The  ftremrth  of  the  arteries  is  confider- 

O 

able  enough : but  the  denfe,  hard  texture  of  the 
outer  cellular  coat,  as  it  refufes  to  yield  to  a dif- 
tending  force,  breaks  without  much  difficulty,  al- 
moft more  eafiiy  than  the  coats  of  the  veins  ; hence 
arife  aneurifms.  The  trunks  are  almoft  every 
where  weaker,  and  the  branches  ftronger,  fo  that 
the  impulfe  of  the  blood  may  have  confiderable  ef- 
feef  upon  the  former,  while  in  the  limbs  it  has  ve- 
ry little.  Hence,  aneurifm.s,  are  moft  frequent 
near  the  heart.  In  the  lower  extremities,  the 
flrength  of  the  arteries,  and  of  the  veins,  is  increaf- 
ed, as  well  as  in  the  fecretintr  ora;ans. 

XXXV.  Nature  has  diilributed  arteries  over  the 
whole  animal  body,  excepting  a membranes, 
where  they  iirc/e  not  yet  been.demonftrateJ.  But 

fhe 


Chap.  II. 


VESSELS. 


15 

Ihe  has  difpofed  of  the  trunks  every  where  in  pla- 
ces of  fafety,  becaufe  wounds  cannot  happen  to 
the  fmaU  ones  without  danger,  or  to  the  large  ones 
without  lofs  of  life.  The  Ikin  has  numerous  fliort 
and  fmaU  tvdgs  ; but  the  larger  trunks,  defended 
by  the  fldn  and  mufcles,  creep  near  the  bones. 
In  general,  the  arteries  are  in  proportion  to  the 
parts  of  the  body  to  which  they  are  fent,  yet  lar- 
ger branches  go  to  the  fecretory  organs,  fpleen  and 
brain  *,  and  finaller  ones  to  the  mufcular  parts. 

XXXVI.  The  proportion  of  the  folid  part  of  an 
artery  to  its  cavity,  is  not  every  where  the  fame, 
nor  is  it  conftant  even  in  the  fame  artery.  This 
proportion,  in  the  firft  place,  is  leaf:  of  all  at  the 
heart,  and  increafes  as  the  arteries  remove  farther 
from  it.  Secondly,  in  a fuU  fed  plethoric  animal, 
whofe  blood  paifes  freely,  and  with  great  force, 
through  its  arteries,  the  proportion  of  the  folid 
part  is  lefs  than  in  a familhed  extenuated  creature, 
whofe  blood  moves  feebly. 

XXXVII.  From  each  arterial  trunk,  branches  are 
fent  forth,  and  from  thefe  again  proceed  fmaUer 
ramifications  by  repeated  divifions,  of  which  you 
will  fcarcely  find  the  end,  though  you  may,  per- 
haps, trace  a feries  of  twenty.  The  calibers  of 
any  two  branches  taken  together,  always  exceed 
that  of  the  trunk  from  whence  they  come,  in 
nearly  a fefquilateral  proportion,  or  fomewhat 
lefs.  In  the  capillaries  this  law  does  not  obtain, 
and  the  fum  of  the  calibers  of  the  branches,  does 
not  exceed  that  of  the  trunk.  The  fmaUeft  ar- 
teries v/hich  tranfmit  a fingle  globule,  have  near- 
ly the  fame  diameter  with  a globule,  that  is,  the 
three  thoufandth  part  of  an  inch.  Every  trunk, 
above  its  divifion,  expands  a little.  The  angles, 
at  which  the  branches  go  out,  are  generally  a- 
cute,  either  half  right  angles  or  nearly  fo  j which 
angle,  even  in  mechanics,  carries  projefililes  far- 
theft.  Inftances  of  their  going  off  at  right  angles, 

or 


VESSELS. 


Chap.  IL 


i6 

or  nearly  fo,  we  have  in  the  lumbar  and  intercof- 
tal  arteries ; of  a retrogade  courfc,  we  have  one 
iidtance  in  the  coronaries  of  the  heart,  and  another 
in  the  fpinal  arteries,  which  are  produced  by  the 
a^ertebrals,  and  feveral  in  thofe  of  the  limbs,  as  in 
the  tibial  and  brachial.  But  nioft  of  thofe  v hich 
are  efLceined  retrograde,  are  fent  oft,  at  their  ori- 
gin, at  acute  angles  ; fuch  as  the  afeending  artery 
of  the  pharynx,  the  defeending  one  of  the  palate, 
the  umbilical  and  mammary  arteries,  and  the  nu- 
tritious ones  of  the  large  bones.  Befides,  it  is  com- 
mon for  larger  branches  to  arife  under  lefs  angles, 
and  fmaller  ones  under  greater  angles.  It  is  rare 
that  two  arteries  of  a large  diameter  run  together 
into  one  trunk.  An  example  of  this,  liowever, 
odds  in  the  artery  formed  of  the  vertebrals.  In 
the  fmaller  ones  it  is  frequent,  as  in  both  the  fpi- 
nal arteries,  and  that  of  the  fincipital  foramen. 
In  many  parts,  they  have  repeated  flexures,  fo  that 
the  artery  undulates  around  a ftraight  line,  in  al- 
ternate obtufe  angles.  This  happens  moft  fre- 
quently vcherever  the  diameter  of  the  part  to  which 
the  artery  goes,  is  occaflonally  much  increafed,  as 
in  the  large  intcftincs,  womb,  face,  fpleen,  lips, 
and  iris.  Even  the  ftraight  arteries  in  other  pla- 
ces, if  too  much  diftended,  fall  into  ferpentine 
flexures.  Sometim.es  they  are  fuddenly  twifted 
into  a Idnd  of  circle,  as  the  carotids  under  the 
mammillary  prccefs. 

XXXVIII.  They  are  frequently  conjoined  by  in- 
termediate branches,  in  fuch  a manner,  that  the 
twig  of  one  artery  lhall  run  to  meet  one  of  the 
fame  kind,  from  a neighbouring  artery,  and 
unite  with  it  into  one  trunk.  Wc  find  inltanccs 
of  this,  in  large  trunks  in  the  inteftines,  among 
the  middling  ores  in  the  kidneys,  womb,  <kc. 
and  amon<r  the  fmaller  ones  in  ail  narts  of  the 
body;  fo  tliat  there  is  no  part  of  the  human 
body,  in  whicli  tlie  neighbouring  arterial  branches, 

whether 


Chap.  IL 


VESSELS. 


17 

whether  of  the  fame  or  of  different  denominations, 
are  not  joined  by  intermediate  branches.  Of  cir- 
cles formed  by  arteries  diverging  laterally,  and 
uniting  again  with  each  other,  we  have  inftances 
in  the  eye  and  brain.  The  extremeties  of  the  arte- 
ries which  are  either  cylindrical  or  nearly  fo,  fend 
off  fmaller  branches,  which,  in  the  fame  extent, 
are  more  numerous,  and  are  generally  reticular  ; 
fo  that  each  branch,  by  its  fmaller  twigs,  forms  ana- 
ftomofes  with  thofe  of  its  neighbouring  branches  : 
and  thus  we  find  it  in  aU  membranes.  By  this 
means  it  happens,  that,  though  the  paffage  from  the 
heart  to  any  part  of  an  artery  be  obftrufted,  the 
blood  may  neverthelefs  flowthrough  the  neighbour- 
ing arteries  into  all  the  branches  of  the  obfl;ru(S:ed 
one.  Thus,  gangrene  and  langour  are  very  power- 
fully prevented,  and  obftrucflions  are  more  eafily 
refolved  by  the  repulfion  of  the  obftacles  into  the 
larger  part  of  the  trunk. 

XXXIX.  Laftly,  the  minute  arteries  terminate  in 
veins,  either  by  a continuation  of  their  canals,  fo 
that  the  ultimate  little  artery,  which  is  general- 
ly refledfed,  having  pafled  the  angle  of  its  re- 
flection, has  now  become  a fmall  vein  ; or  elfe  a 
branch,  fent  out  at  right  angles  from  the  artery,  is 
inferred  under  a like  angle  into  the  branch  of  a fmall 
vein.  Both  thefe  kinds  of  mechanifm  are  demon- 
ftrated  to  us  by  the  microfcope,  and  by  the  eafy  re- 
turn through  the  veins,of  injedlions  thrown  into  the 
arteries.  Thefe  veflels  are  fometimes  large  enough 
to  receive  feveral  globules,  and  fometimes  admit  on- 
ly one.  A large  artery  never  terminates  in  a vein. 

XL.  In  the  vifcera  we  do  not  find  their  diftribu- 
tion  fo  truly  reticular  but  varied,  the  fmall  branches 
defcending,  crov/ded  together,  brufhy,  arbufcular, 
parallel  to  the  trunk,  ferpentine  or  villous,  accord- 
ing to  the  various  natures  of  the  parts. 

XLi.  Sometimes  the  arteries  end  in  another  man- 
ner, namely,  by  being  converted  into  veflels  of  fmall- 
C er 


VESSELS. 


Chap.  II. 


er  orders.  Thefe  are  fometimes  continuous  with 
the  arteries  and  are  real  trunks,  as  in  the  oph- 
thalmic artery,  if  you  examine  the  arteries  of  the 
tunica  choroides,  then  the  circle  of  the  uvea, 
and  laftly,  the  colourlefs  ones  of  the  iris.  That  a 
netveork  of  pellucid  arteries  is  continuous  with  the 
red  branches  in  the  tunica  conjunctiva,  is  evident 
from  inflammation,  and  the  rednefs  of  the  part 
when  relaxed  by  vapour,  or  by  cupping,  from  in- 
jection, and  the  microfcopical  obfertutions  of  Lie- 
berkuhn  upon  frogs,  in  which  colourlefs  globules 
Vv'ere  feen  to  pafs  from  red  arteries  into  lateral 
velfels.  In  a fabric  of  this  kind,  the  red  blood  is 
eafily  forced  into  the  fmaller  vefl’els. 

XLii.  In  other  places  the  fmaller  velfels  feem  to 
proceed  laterally  from  the  trunks  of  the  lc?dt  fan- 
guiferous  arteries,  as  brandies  fmaller  than  the 
trunks.  Thefe  are  called  Excretory  Duclrs.  It  is 
with  difliculty  that  thefe  are  filled  through  the  red 
velfels  ; of  this  Ave  hai'e,  however,  examples  in  the 
kidneys,  tli.e  liver,  and  breaks.  And  the  blood, 
wEen  vitiated,  penetrates  the  excretory  duds  of 
the  whole  body  without  hurting  the  velfels,  lince 
tliat  aberration  has  no  bad  confequence. 

XLiii.  Another  termination  of  arteries  is  in  ex- 
haling A^eflels  ; and  this  is  frequent  in  ali  parts  of 
the  body.  Tlie  whole  Ikin,  all  the  membranes  of 
the  human  body  vdiich  inclofe  any  cavity,  all  the 
ventricles  of  the  brain,  both  chambers  of  the  eye, 
all  the  adipofe  cells  and  pulmonary  A^elicles,  the 
whole  cavity  of  the  ftomach  and  inteftinal  tube 
and  air  pafl'ages,  are  all  of  them  rcpleniflied  with 
exhaling  arteries  of  this  kind.  Thefe  emit  a thin, 
Avatery,  gelatinous  humour,  A\'hich,  by  ftagna- 
tion,  congeftion,  and  accumulation,  from  difeafe  or 
death,  is  conA’^erted  into  a AAutery,  but  coagulable 
lymph.  The  truth  of  this  is  eanly  demonftrable 
from  the  exudatioii  that  enfues  from  injecting  the 
arteries  AA'itli  A\ann  AA'ater.  In  feme  places,  in- 
deed, 


Chap.  II. 


VESSELS. 


19 


‘ deed,  they  pour  out,  not  a thin,  vapour,  but  blood 
itfelf,  as  we  fee  in  the  heart,  the  cells  of  the  penis, 
urethra,  clitoris,  and  nipple  of  the  female  breaft  j 
in  all  which  the  blood  itfelf  is  poured  out  in  its 
natural  ftate.  Is  not  every  fecretion  in  true  glands 
or  cryptse,  analogous  to  this  exhaling  fabric  ? 

XLiv.  In  every  part  of  the  human  body,  do  vef- 
fels  arifmg  from  the  fanguiferous  ones,  but  carry- 
ing a humour  thinner  than  blood,  again  fend  out 
other  fmalier  veffels,  to  be  fubdivided  into  ftill 
lefs  orders  ? We  feem,  indeed,  not  to  want  ex- 
amples of  this,  as  pointed  out  by  men  of  eminence. 
That  the  aqueous  humour  is  fecreted  by  minute 
veifels,  generated  from  the  colourlefs  arteries  of 
the  iris,  is  very  probable.  That  the  red  coloured 
veifels  in  the  cortical  fubftance  of  the  brain,  by 
the  intervention  of  another  order  of  veifels,  fepa- 
rate  a juice  pervading  the  medullary  fubftance,  is 
almoft  certain.  Eryftpelas,  and  the  yellow  inflam- 
mation, arifmg  from  the  yellow  or  ferous  globules 
impafled  into  fmalier  veifels,  fuggeft  the  fame 
opinion. 

XLv.  Are  there  then  yellow  arterial  veifels  of  a 
fecond  order,  which  fend  off"  lymphatic  ones  of  a 
third,  from  whence,  by  degrees,  ftill  lefs  kinds  of 
veifels  branch  out  ? Such  a fabric  does  not  feem 
agreeable  to  the  eafy  tranfition  of  blood,  mercury, 
or  wax,  into  the  exhaling,  perfpirative,  uriniferous 
and  adipofe  veifels  and  pulmonary  cells  ; nor  is  it 
very  difficult  for  the  blood  to  ftray  into  the  laftif- 
erous,  lymphatic,  and  lachrymal  veifels,  whither 
it  fliould  feem  not  able  to  penetrate,  if  it  went 
through  any  other  intermediate  vafcular  fyftem, 
fmalier  than  the  blood-globules.  Nor  is  this  opi- 
nion admiffible,  from  the  great  retardation  which 
muft  arife  to  the  humours  in  a third,  and  much 
more  in  inferior  orders  of  veffels. 

XL VI.  The  Veins,  in  many  particulars,  rcfem- 
ble  the  arteries.  There  are  fix,  of  which  two  an- 
fwer  to  the  aorta,  and  the  remaining  four  to  the 
c 2 pulmonary 


20 


VESSELS. 


Chap.  II. 


pulmonary  artery.  Their  balls  is  in  the  ventricles ' 
of  the  heart,  and  their  apices  in  the  extremity  of 
each  branch,  through  all  p^rts  of  the  body,  ex- 
cepting one  inftance,  in  the  liver.  In  moft  parts, 
they  run  parallel  with  the  arteries,  contiguous  to 
them  ; but  they  differ  in  various  refpects. 

XLvn.  The  fabric  of  the  veins  is  thin,  every 
where  fmooth,  difficultly  feparable  into  membranes ; 
of  which  the  inmofl;  is  like  that  of  the  arteries, 
and  round  it  is  a condenfed,  but  very  eaffiy  dif- 
tended,  cellular  membrane,  furrounded  in  a fingle 
inftance,  above  and  below  the  heart,  with  tranf- 
verfe  mufcular  fibres.  The  cellular  lubftance, 
which  connects  them  to  the  reft  of  the  body,  is, 
however,  like  that  of  the  arteries, every  vffiere  very 
lax.  Notwithftanding  this  ftender  fabric,  the  veins 
are  every  where  fufficiently  firm,  and  do  not  eaffiy 
burft  when  inflated  with  air  ; being,  in  mmft  in- 
ftanceS,  ftronuer  than  the  arteries  themfelves.  But 
they  burft  more  eaffiy  in  man  while  alive,  as  ap- 
pears from  morbid  inftances  in  the  leg,  arm,  face, 
&c.  Nor  do  they  fupport  themfelves  after  being 
divided,  but  collapfe  fo  as  to  make  their  apertures 
appear  like  hits  ; unlefs  they  be  prevented  by 
fome  ftrong  cellular  fubftance  placed  round  them, 
as  we  fee  in  the  liver  and  womb.  They  are  mod- 
erately irritable,  and  not  by  ftimuli  alone,  unlefs 
they  be  chemical ; but,  in  that  cafe,  they  contract 
more  than  the  arteries.  They  have  no  pulfation, 
unlefs,  if  we  may  truft  ail  accounts,  when  the  ve- 
nous channel  is  fomewhere  obftrudfed;  or  when,  in 
dying  people,  the  blood  is  thrown  back  again  from 
the  rig^ht  auricle  into  the  defeendinsr  and  afeend- 
mg  cava,  or  falls  back  from  the  brain. 

XLviii.  The  veins  are  much  larger  than  their  cor- 
refponding  arteries,  having  the  fquare  of  their  dia- 
meter often  double  or  triple  that  of  the  latter  ; and 
fometimes  almoft  quadruple, as  near  the  root  of, and 
in  the  veficls  of  the  kidneys.  In  general,  however, 

tlie 


Chap.  II. 


VESSELS. 


21 


tiie  diameter  of  the  veins  is  to  that  of  the  arteries  as 
nine  to  four  ; yet  the  capacity  of  the  capiliary 
veins  but  little  exceeds  that  of  the  arteries  which 
accompany  them.  They  differ  iikev/ife  from  the 
arteries  in  their  divifion,  having  more  numerous 
trunks  and  branches  ; for  to  one  artery  in  the 
limbs  we  ufually  meet  with  two  veins.  The  lar- 
ger veins  are  alfo  more  reticulated,  and  unite  by 
more  frequent  anaftom.ofes,  not  only  of  the  fmall 
branches,  but  even  of  the  large  trunks,  occurring 
every  where  amongft  the  neighbouring  veins,  up- 
per with  lower,  and  right  with  left.  They  prefer 
the  furface  of  the  body  ; and  through  the  limbs, 
neck,  and  head,  they  run  a long  way,  perfectly  cu- 
taneous, which  is  very  rarely  the  cafe  with  arte- 
ries ; from  which,  on  that  account,  they  feparate. 
Then  the  veins  follow  the  furface,  without  a cor- 
refponding  artery,  which,  in  the  mean  time,  runs 
at  a coniiderable  depth,  attended  by  fome  frnaller 
venous  branch.  In  the  frnaller  branches,  and 
membranous  reticulations,  and  in  the  internal  fa- 
bric of  the  vifcera,  the  veins  and  arteries  common- 
ly run  contiguous.  The  veins  are  generally  iefs 
tortuous. 

xLix.  In  the  larger  fanguiferous  veins,  valves 
are  found  in  great  numbers.  The  innermoft  mem- 
brane rifes  double  into  the  cavity  of  the  vein,  in 
the  manner  of  a curtain,  and  being  on  either  hde 
extended  deeper  along  the  courfe  of  the  vein, 
forms  what  may  be  called  its  cornicles  : but  the 
bafis,  where  it  arifes  from  the  vein  in  the  lhape  of 
a fegment  of  a circle,  is  ftronger,  and  confdtutes 
its  agger.  With  the  lides  of  the  vein  as  it  pro- 
ceeds, they  inclofe  a curtained  fpace,  of  which  the 
exterior  fide  is  the  vein  itfelf,  and  the  interior  the 
valve,  which  by  its  convexity  projects  into  the  cav- 
ity of  the  vein.  The  bafis  of  this  almoil  parabo- 
lic fpace,  or  the  mouth  of  the  valvular  cavity  of 
the  veins,  ahvays  looks  towards  the  heart.  They 
. a:e 


22 


Chap.  II. 


are  fonrd  in  all  the  habcutancous  veins  of  the 
limbs,  in  tnofc  of  the  neck,  face,  tcng'ue,  and  in 
the  veins  of  the  penis  : at  the  origin  of  the  larger 
branches,  there  a.re  two,  three,  four,  and  fometinies 
five  of  them  together,  which,  however,  is  rare  : 
in  the  fmaller  branches  they  are  ilngle.  There 
are  none  in  the  veins  of  the  deep  feated  vifeera ; 
and,  therefore,  none  in  the  brain,  lungs,  heart,  or 
liver,  or  in  the  whole  lyftem  of  the  vena  portarum, 
or  in  the  kidneys  or  womb,  (except  one  or  two 
valves  in  the  fpermatic  vein  ;)  or,  laftly,  in  thofe 
fmalier  veins,  which  a,re  lefs  than  a line  in  diame- 
ter. Sometimes,  though  rarely,  they  have  been 
feen  in  the  vena  azygos.  In  the  cava,  at  the 
mouths  of  the  hepatic  and  renal  veins,  I have 
obferved  a fort  of  wrinkles  in  their  place.  In  the 
fmaller  branches,  the  folitary  valves  are  long  and 
very  acutely  parabolical,  almoll  proportionately 
longer  as  the  vein  is  fmaller.  Thefe  feem  to  op- 
pofe  the  rehux  of  the  blood  more  powerfully  than 
the  larger  ones. 

L.  The  origin  of  the  veins  we  noticed  in  fpeak- 
ing  of  the  arteries.  They  arife  continuous  from 
minute  arteries,  by  inferred  branches,  or  the  re- 
fieclion  of  a trunk.  Others,  again,  are  cither 
continued  from  veins  of  inferior  orders,  or  receive 
additions  and  roots  from  them  ; as,  for  inftance,  in 
the  lymphatic  veilcls  and  thoracic  duel.  Others  of 
a bibulous  kind  take  their  origin  from  the  ab- 
forbing  veins  difperfed  over  the  whole  bodv,  in 
the  cavities  of  the  eyes,  inteftines,  breaft,  perito- 
naeum, pericardium,  and  ventricles  of  the  brain. 
Hence  the  venous  exudation, eafilyirnitablcover  the 
whole  human  body,  by  injecting  the  venous  trunks 
with  an  aqueous  liquor  ; hence  water,  jelly,  or  oil, 
pals  from  the  vena  portarum  into  the  cavity  of  the 
inteftines  ; hence  water,  iniccled  into  the  abdomen 
of  a li  ving  animal  j quickly  difappears.  But  of  thefe 


Chap  II. 


VI 


23 


things  we  liiall  fpeak  again  more  fully  in  their 
pioper  places. 

LI.  Little  different  are  thofe  veins  which  arife 
from  every  part  of  the  cellular  membrane,  and  car- 
ry back  to  the  mafs  of  blood,  dropfical  waters,  moift 
vapours,  diffolved  fat,  extravafated  and  corrupting 
blood,  and  the  poifon  of  opium  introduced  into  the 
cellular  texture  ; or  bring  back  the  blood  itfelf 
from  the  cellular  fabric  of  the  penis,  clitoris,  or 
nipples  of  the  breaks,  after  the  venereal  orgafm. 
That,  into  all  the  glands,  veins  of  this  kind  open, 
is  highly  probable,  which,  by  abforbing  the  thin- 
ner humour,  leave  the  remaining  mafs  of  a thicker 
confiftence,  as,  for  example,  the  bile,  fperm,  mu- 
cus, &c. 

Lii.  That  there  are  fmaller  orders  of  veins,  as 
of  arteries,  refembling  thofe  which  convey  blood, 
appears  from  experiments.  Thus,  in  the  eye  there 
are  the  fmall  veins  of  the  iris,  and  not  a few  trunks 
in  the  adnata  ; and,  without  doubt,  veins  return 
from  the  vitreous  humour,  which,  in  health,  are 
pellucid. 

Liii.  But,  in  moft  parts  of  the  human  body,  other 
veins  are  found,  full  of  a reddirn,  yellowifh,  or  al- 
moft  pellucid  liquor,  coagulable  by  heat  ; formed 
of  a very  tender  coat,  and  excitable  by  chemical  fti- 
muli.  They  are  intercepted  by  double  valves,  for  the 
moft  part  fo  very  frequently,  that  they  ahnoft  feem 
jointed  when  they  are  turgid.  By  degrees  uniting, 
either  the  whole  or  greateft  part  of  them  meet  in 
the  thoracic  duel.  They  arife  from  the  cellular 
texture  throughout  the  whole  body,  as  I had  long 
ago  learned  of  the  lactiferous  veflels  of  the  breafts, 
the  vafa  efferentia  of  the  tefticles,  and,  laftly,  of  the 
lymphatics  originating  from  the  mefenteric  glands ; 
and  is  now  ftiewn  of  the  lymphatic  veflels  of  the  tef- 
ticles, fpleen,  and  other  parts.  From  analogy,  and 
from  the  analogy  of  difeafes,  efpecially  of  clrop- 
fy,  we  are  induced  to  believe,  tiiat  they  arife  like- 

r* 

wiie 


24 


VESSELS. 


Chap.  II. 


wife  from  the  large  cavities  of  the  body  ; nor  is  it 
contradiftory  to  iuppofe.  that  titis  kind  of  vcffels 
receive  a thin  hmnonr  from  very  minute  veins. 
But  all  the  lymphatics,  in  their  courfe,  meet  with 
a peculiar  kind  of  glands,  called  Conglobate,  into 
which  they  enter,  having  become  arterial  by  the 
convergence  of  the  venous  cones,  and  dividing  into 
branches  ; and  again  iuue  from  them,  to  unite  into 
new  trunks. 

Liv.  Thefe  glands  themfelves  confift  of  lympha- 
tic veffels,  connected  by  cellular  texture,  into  which 
a fluid  brought  by  the  arteries,  exfudes,  and  from 
which  it  is  taken  up  by  the  veflels  which  carry 
away  the  lymph.  They  are  covered  with  a contin- 
uous mem.brane,  generally  of  an  oval  fliape,  wheth- 
er they  are  Ample  or  compound;  and  they  follow 
the  courfe  of  the  larger  blood-veflels ; efpecially  of 
the  veins,  through  the  whole  trunk  of  the  body, 
to  the  infertions  of  the  limbs  ; running  along  the 
jugular  and  fubclavian  veins,  the  vena  cava  fupe- 
rior,  the  afpera  arteria,  gullet,  lumbal  vena  cava, 
vena  porta,  the  iliac,  hypogaftric,  crural  and  popli- 
teal veins,  and  likewife  the  veflels  of  the  ftomach, 
fpleen,  n^efentery,  and  mefocolon. 

Lv.  They  are  found  on  the  furface  of  the  vifee- 
ra,  in  the  thorax  and  abdomen  : and  more  eaAly  in 
brutes  : in  the  lower  part  of  the  face,  mufcles  of 
the  tongue  and  parts  adjacent,  in  the  neck,  and 
thofe  parts  of  the  upper  limbs  which  are  nearefl; 
the  trunk,  as  far  as  the  bending  of’  the  elbow  ; 
throu2:hout  the  whole  lens;th  of  the  anterior  and 
pofterior  inediaftinum,  and  wherever  we  And  con- 
globate glandules,  either  in  the  neck  or  thorax  ; in 
th'e  whole  lumbal  region  that  is  contio;uous  to  the 
aorta;  in  the  mefocolon  ^pelvis,  vcffels  and  furface  ot 
the  teflicle  ; and  in  the  lower  limbs,  wherever  they 
are  fupplied  with  conglobate  glandules,  as  far  as  the 
knees.  Whether  thev  extend  further,  and  exift  in 
every  part  of  the  body,  in  the  brain,  eye,  hand, 


3 


Chap.  II. 


VESSELS. 


25 

foot,  back,  fore  part  of  the  perlton3euiTi,  &c.  is  not 
confirmed  by  fuiliciently  accurate  or  numerous  ob- 
fervations  on  the  human  body.  They  are  every 
where  found  on  the  furfaces  of  the  vifcera.  They 
are  almofi;  every  where  collected  into  bundles, 
which  lie  not  far  from  the  large  blood-veflTels.  Thofe 
from  the  inferior  limbs,  pelvis,  and  loins,  run  into 
one  duel,  which  is  joined  by  another  bundle  coming 
from  the  liver,  fpleen, and  ftomach ; and  that  trunk, 
at  length,  becomes  the  thoracic  du£l.  The  fuperior 
veiTels,  from  the  whole  extent  of  the  breaft,  the 
• head,  and  fuperior  limbs, empty  themfelves  into  the 
fame  duct  towards  its  upper  extremity.  They 
feem,  however,  likewife  to  terminate  in  the  red 
veins. 

Lvi.  Of  what  fervice  thefe  glands  are  to  the  lym- 
phatic vefiTels  is  not  yet  well  known.  In  the  foetus, 
as  well  as  the  thymus  and  glandulas  renales,  they 
are  turgid  with  a milky  liquor  ; but  it  is  not  certain 
that  this  fluid  is  poured  out  into  the  cellular 
fpaces.  It  is  however  rendered  probable  by  late 
experiments,  that  in  thefe  glands  fome  kind  of  fluid 
is  prepared  which  is  mixed  with  the  lymph  ; fince 
thin  fluids,  injefted  into  the  a.rteris,  enter  the  lym- 
phatic veflels.  In  the  progrefs  of  life,  this  fluid  van- 
ifhes  ; and  the  glands  themfelves,  being  dried  up, 
almoft  difappear.  The  very  frequent  fchirrofities 
in  thefe  glands  feem  to  indicate,  that  the  motion 
of  the  fluid  paffing  through  them  is  retarded. 

Lvii.  Their  valves  (liii.)  are  compofed  of  two 
femicircular  membranes,  which  give  way  to  the 
fluid  that  goes  toward  the  1 vrger  trunks  ; and  by 
applying  themfelves  to  the  fides  of  the  veffel,  leave 
a free  pafiTage.  But  the  fame  valves,  if  the  liquor 
return  from  a larger  trunk  towards  the  fmaller 
branches,  being  filled,  fwell,  expamd,  and  fliut  up 
the  tube. 


CHAP. 


2$ 


CIRCULATION. 


Chap.  III. 


CHAP.  III. 

OF  TPIE  CIRCULATION  OR  MOTION  OF  THE  BLttOD 
TI-IROUGII  THE  ARTERIES  AND  VEINS. 

Lviii.  I ''HE  arteries  and  veins  hitherto  deferi- 
I bed,  contain  either  blood  or  lymph. 
The  red  blood,  v.diofe  nature  v'e  Ihall  explain  when 
we  treat  of  fecretion,  fills  the  arteries  and  veins 
commonly  known,  which  we  call  red,  or  thofe  of 
the  hrll  order,  and  which  have  their  origin  in  the  • 
heart.  Thefe  it  fills,  in  a living  perfon,  in  fuch  a 
manner  that  at  one  time  they  are  very  loofely  and 
imperfectly  difiiended  by  it,  and  at  another,  they 
are  rendered  very  full  and  turgid.  After  death, 
the  veins  are  found  very  full  of  blood ; but  occa- 
fionally,  the  fmall  veins,  chiefly  feme  time  after 
death,  have  been  found  diftended  with  air.  The 
arteries  in  the  dead  body,  commonly  contain  only 
a fmafl  quantity  of  blood. 

Lix.  This  blood  is  rapidly  moved  through  all  the 
veffels  of  the  living  body.  The  truth  of  which  is 
demonftrated  by  wounds,  from  which,  even  a mor- 
tal lofs  of  as  much  blood  as  is  neceflai*^'  for  the  main- 
tenance  of  life  quickly  enfues,  almoft  inftantly  from 
the  larger  arteries,  and  fometimes  very  fuddcnly 
from  the  fmaller  ones,  but  more  diflicultly  from  the 
veins,  unlefs  very  large  ; yet  are  there  not  want- 
ing inflances  of  fatal  hemorrhages  from  wounds 
of  the  vein  in  the  inner  corner  of  the  eve,  or  of 
that  under  the  tongue.  Laftly,  experiments  made 
upon  liHng  animals,  fufliciently  prove  the  power- 
ful impulfe  with  which  the  blood  is  moved,  partic- 
ularly through  the  arteries.  In  the  large  arteries 
it  runs  moft  fwiftly ; in  the  fmall  ones,  fomewhat 
flower.  In  the  large  veins,  the  blood  moves  more 
flowly  than  in  the  arteries,  in  the  lame  proportion 
as  the  calibers  of  the  arteries  are  ieis  tlian  thofe  of 


Chap.  III. 


CIRCULATION. 


^7 

the  veins,  almoft  twice  or  thrice.  Another  argu- 
ment is  derived  from  the  compreliion  and  relaxa- 
tion of  a vein,  by  which  the  motion  of  the  blood  is 
promoted  from  valve  to  valve.  This  motion  in  the 
veins,  is  equable  enough  ; but,  in  the  arteries,  it  is 
alternately  greater,  fo  that  the  veffel  at  one  inftant 
rebounds  llrongly,  and  at  the  next  is  relaxed.  This 
is  confirmed  in  living  animals  by  ocular  infpeclion. 

LX.  The  direction  of  the  motion  of  the  blood 
through  the  red  veflTels,  is  Iliewn  by  experiments 
of  this  kind.  Firft,  it  is  certain,  that  all  the  arte- 
ries and  veins  communicate  ; becaufe,  from  one, 
and  often  a fmall  artery,  and  fometimes  alfo  from 
a vein,  all  the  blood  ihall  be  difcharged,  even  cauf- 
ing  death  and  extreme  pallidity  of  the  whole  flefli, 
not  only  of  the  limb  wounded,  but  of  the  whole 
body.  Fatal  examples  have  occurred  from  arteries 
of  the  noftrils,  gums,  fingers,  teeth,  from  a cuta- 
neous pore,  lachrymal  point,  cupping,  and  the  bite 
of  a leech.  There  miufl;  therefore  be  pafifages  by 
which  the  blood  fpeedily  flows  from  the  venous 
into  the  arterial  fyfcem. 

Lxi.  That  the  blood,  again,  in  the  arteries,  flows 
from  the  heart  toward  the  extreme  parts  of  the 
body,  is  proved  by  the  microfcope,  and  by  tying 
up  the  artery  of  a living  animal.  For  if  an  artery 
be  flopped  by  a ligature,  a fwelling  enfues  in  that 
part  betwixt  the  heart  and  the  ligature,  whilft 
the  other  part  beyond  the  ligature,  and  more  re- 
mote from  the  heart,  becomes  empty,  has  no  pul- 
fation,  nor,  if  wounded,  bleeds.  The  effect  of  a 
ligature  is  alfo  produced  by  difeafe  ; as  when  fome 
tumor,  by  ccmprefiion,  or  an  aneurifm,  intercepts 
the  motion  of  the  heart.  Experiments  have  been 
made  on  moft  of  the  arteries  even  by  myfelf. 
Sometimes  anaflomofes,  or  the  efcape  of  the  blood 
by  fome  channel  into  a neighbouring  branch,  and 
the  retrocefiion  of  the  blood  in  a dying  animal, 
feeni  exceptions» 


CIRCULATION. 


Chap.  III. 


2S 

Lxii.  Tliere  have  been  doubts  with  regard  to 
the  motion  of  the  venous  blood,  and  all  the  an- 
cients were  perfuaded,  that  the  blood  flow'ed  alfo 
in  the  veins  from  the  heart,  or  certainly  from  the 
liver,  to  all  parts  of  the  body.  Few  have  difeovered 
the  error  : feveral,  indeed,  in  the  pulmonary  vein  : 
in  the  vena  cava,  fewer  ; perhaps  only  Andreas  Cse- 
falpinus,  and  as  an  uncommon  appearance,  Vefalius. 

Lxiii.  Hai'vey  firft  eftabliilied,  by  experiments, 
the  courfe  of  the  venous  blood  which  returns  from 
every  part  to  the  heart,  fo  as  to  remove  every 
doubt.  And,  firft,  the  valves  point  out  this  truth  ; 
for  the  common  ofiice  of  thefe  valves  is,  that  every 
prefliire,  however  applied  to  the  veins,  determines 
the  blood  towards  the  heart,  fince  they  take  away 
the  pofiibility  of  its  returning  into  the  branches, 
after  having  once  entered  a trunk.  For,  fince  the 
valvular  portions  are  concave  upwards,  towards  the 
heart,  the  refluent  blood  enters  into  and  expands 
them.  Thus,  that  part  of  the  valve  which  projects 
loofely  within  the  cavity  of  the  vein,  approaches 
towards  the  axis,  until  it  meet  the  eppofite  fide, 
and  ihut  up  the  tube.  This  we  know  from  infla- 
tion, ligatures,  and  injections ; for  we  never  can 
force  a liquor  eafily  into  the  veins  againft  the  valves. 
They  do  not,  indeed,  every  where  fliut  up  the 
cavity  entirely  ; but  they  always  do  it  in  a great 
meafare. 

LXiv.  Another  olnce  of  the  valves  in  the  veins 
feems  to  be  to  fuftain  the  weight  of  the  blood,  that 
its  upper  columns  may  not  gravitate  upon  the  lower, 
nor  the  blood,  flowing  through  the  trunks,  impede 
that  comino:  throuarh  the  branches.  For  if,  from 
the  flower  motion  of  the  blood,  it  flrall  happen  that 
its  weight  flrall  bear  too  great  a proportion  to  the 
impullive  force,  and  any  part  of  the  fangaiineous  col- 
umn begin  to  deicend  by  its  weight,  the  ncareft 
valve  fupports  it  in  its  relapfe,  prevents  it  from 
preifing  on  the  lucceeding  column,  and  affords  time 


Chap.  IH. 


CIRCULATION. 


29 


for  fome  contiguous  mufcle,  by  its  preffurs,  to  free 
the  valve,  and  propel  the  column.  This  is  the  rea- 
fon  for  the  lituation  of  valves  in  the  veins  of  the 
limbs  and  neck ; in  which  parts  they  are  both  more 
numerousand more  robuft thanelfewhere.  Thisalfo 
explains  the  caufe  of  varices,  when  the  blood,  enter- 
in  the  valves,  preffes  their  folid  convexity  down- 
wards, and  forces  them  to  defcend  and  dilate.  Like- 
wife,  in  mufcular  motion,  the  valves  occafion  the 
whole  preffure  which  the  veins  then  fuftain,  to  for- 
ward the  due  courfe  of  the  blood  towards  the  heart. 

Lxv.  Moreover, the  valves  placed  in  the  right  fide 
of  the  heart,  are  fo  conftrufted,  as  we  fhall  here- 
after fee,  that  they  freely  permit  blood,  air,  or  wax, 
to  pafs  from  the  venous  trunks  of  the  cava  into  the 
heart,  but  allow  nothing  to  efcape  from  the  heart. 

Lxvi.  Befides,  in  a living  perfon,  ligatures  make 
the  thing  evident.  When  either  by  defign  or  ac- 
cident, the  veins  of  the  ham,  arm,  or  leg,  are  tied 
with  the  limb  jitfelf,  the  limb  every  where  below 
the  ligature  fwells,  the  veins  become  diftended  and 
turgid,  and,  when  opened,  freely  difcharge  blood ; 
nothing  of  this  kind  happens  above  the  ligature, 
nor  are  any  veins  to  be  feen  there.  The  fame  hap- 
pens when  the  veins  are  compreffed  by  fchirrous 
vifcera,  or  enlarged  glans ; and  from  polypi,  tumors 
of  the  large  veins  are  frequent.  Ligatures  retain 
the  blood  in  any  limb  round  which  they  are  tied,, 
and  prevent  it  from  returning  to  the  heart,  and 
from  being  loft  through  a wound  in  another  part. 

LXVI  I.  The  experiments  which  have  been  made 
on  living  animals,  are  ftill  more  accurate.  From 
them, even  from  our  own,  it  appears, that,  by  tying, 
in  a living  animal,  any  vein,  whether  belonging  to 
the  cava  or  to  the  pulmonary  veins,  that  part  al- 
ways fwells  which  ismoft  remote  from  the  heart, and 
is  diftended  with  the  blood  retained  by  the  obftacle, 
while  that  next  the  heart  becomes  pale  and  flaccid. 
Laftly,  if  both  the  arteries  and  veins  be  tied,  the 

veins 


CIRCULATIDN. 


Chap.  III. 


veins  coilapfe  ; but,  upon  removing  the  ligature, 
the  veins  are  immediately  filled. 

Lxviii.  In  like  manner,  the  injection  of  poifons 
or  medicines  fhews,  that,  into  whatever  vein  you 
inject  chemical  acid  fpirits,  the  blood  even  to  the 
heart  is  coagulated  by  the  force  of  the  poifon.  But 
the  affection  of  the  brain  by  the  narcotic  power  of 
opium,  of  the  inteftines  by  purgatives,  and  of  the 
Ilomach  by  emetics,  clearly  proved  that  the  blood, 
with  which  thefe  fubftances  were  mixed,  had  paff- 
ed  from  the  venous  branch  to  the  heart,  and  from 
thence  through  the  whole  body. 

Lxix.  Moreover,  from  the  transfufion  of  blood, 
it  appears  that  the  living  blood  of  one  animal,  in- 
jected into  the  vein  of  another,  completely  emptied 
of  blood,  replenilhes  its  heart,  arteries  and  veins, 
fo  as  to  reftore  vigour,  turgidity,  and  even  to 
produce  plethora. 

Lxx.  But  that  the  blood  palfes  from  the  minute 
arteries  into  the  minute  veins,  we  .are  taught  by 
injection  ; filling,  without  much  difficulty,  by  one 
arterial  trunk,  the  arteries  and  veins  throughout 
the  whole  body,  provid..ed  the  liquor  be  watery  and 
fiuid  ; and  with  very  great  eafe  thofe  of  the  head, 
mefentery,  heart  and  lungs. 

Lxxi.  Laftly,  microfcopical  obfervations  on  the 
pellucid  tails,  feet  and  mefenteries,  of  animals, 
prove,  beyond  all  doubt,  that  the  blood,  carried  to 
the  extreme  parts  by  the  arteries,  is  poured  either 
into  fmall  veins,  continuous  with  the  reflected  ar- 
teries, or  through  communicating  branches  from 
an  arterial  trunk  into  a parallel  vein,  and  that  it 
returns  by  the  veins  to  the  parts  nearer  the  heart. 
This  tranfition  happens  both  in  the  moft  minute 
veins,  which  are  capable  of  receiving  only  one  glo- 
bule, and  in  thofe  fomewhat  larger,  which  admit 
two  globules.  That  there  is  nowhere  any  fpongy 
or  parenchymatous  fubflance  interpofed  betw’ecn 
the  arteries  and  veins,  is  proved  both  by  the  mi- 

crofeope 


Cpiap.  III. 


CIRCULATION. 


3* 

crofcope  and  by  injeftions,  which,  if  there  were 
any  cellular  fpace  betwixt  the  arteries  and  veins, 
would  be  extravafated  in  fliapelefs  mafles. 

Lxxii.  The  circulation  of  the  blood,  is,  there- 
fore, nov/  received  as  a medical  truth  by  every 
one ; namely,  all  the  blood  of  the  humian  body  is 
carried  through  the  aorta,  from  the  left  cavity  of 
the  heart  towards  the  extremities  of  the  arterial 
branches ; whence  it  is  entirely  tranfmitted  into 
the  minute  veins  ; from  thence  it  returns  to  the 
large  veins,  the  cava  and  heart  itfelf;  in  which 
courfe  it  perpetually  circulates. 

Lxxiii.  Yet  inftances  occur,  when,  from  pallions 
of  the  mind,  from  a fudden  great  revulhon  by 
blood-letting,  or  from  convulhon,  the  blood  has 
retroteded  from  the  fmaUer  into  the  larger  arte- 
ries. And,  in  like  manner,  from  an  obilruclion 
being  formed  in  the  venous  branches  above  the 
valves,  the  blood  has  been  knowm  to  return  into 
the  extreme  branches.  But  thefe  deviations,  are, 
for  the  moft  part,  tranlitory,  and  the  blood  foon 
returns  into  its  natural  courfe.  They  may  be  fup- 
pofed  to  happen  moft  frequently  in  the  abdomen 
and  vena  portarum. 

Lxxiv.  The  courfe  of  the  humours  in  the  val- 
vular lymphatic  veins,  appears  from  ligatures  and 
from  the  valves  : for  every  lymphatic  vein  when 
tied,  fweUs  between  its  fmaller  extremities  and  the 
thoracic  duCt ; but  grows  flaccid  betwixt  the  duft 
and  ligature.  All  the  valves,  like  thofe  of  the 
veins,  allow  air  and  mercury  to  flow  freely  into 
the  thoracic  duct ; but  they  refift,  and  often  obfti- 
nately,  the  contrary  courfe,  although  fometimes 
in  the  dead  body  they  have  given  way. 

Lxxv.  The  vapour  that  moiftens  the  cellular  fub- 
ftance,  the  halitus  of  the  abdomen  and  other  cavi- 
ties are  conveyed  from  the  pellucid  into  the  red 
veins,  that  thefe  may  tranfmit  their  contents  to  the 
heart.  Hence,  v'hen  a vein  is  comprefled  or  tied, 

oedema 


CIRCULATION. 


Chap.  III. 


32 

cedema  enfues,  the  fluid  flagnating,  from  its  paf- 
fage  being  interrupted.  In  the  otlicr  fmaller  vef- 
fels,  experiments  cannot  be  made ; but  reafoning 
and  analogy  fupport  the  fame  concluflon.  Experi- 
ments concerning  the  fluid,  reabforbed  from  the 
inteftines,  pulmonary  veficles  and  Ikin,  fliail  be 
mentioned  in  their  proper  places. 

jLxxvi.  Therefore  all  the  fluids  in  the  human 
body  are  expelled  from  the  heart  into  the  aorta ; 
and  except  thofe  which  are  exhaled  out  of  the  cav- 
ity of  the  body,  or  are  excreted,  they  all  return  to 
the  heart  through  the  minute  veins.  It  remains 
to  difcover  a palfage  by  which  the  blood  may  re- 
turn from  the  right  to  the  left  fide  of  the  heart  ; 
but  this  paflage  luppofes  an  acquaintance  with  the 
hiflory  of  the  heart  and  pulmonary  veflels. 


CHAP.  IV. 

HEART. 

Lxxvii.  ^ g ■'HE  thorax,  compofed  of  bones  and 
I cartilages,  on  the  whole,  refembles 
a truncated  cone,  as  we  fliall  hereafter  mention. 
The  lateral  parts  of  this  cone,  are  two  membranous 
bags,  having  at  their  upper  end  an  obtufe  termina- 
tion, above  the  firfl;  rib,  at  which  place  they  are  con- 
tiguous, and  feparated  only  by  fome  cellular  fub- 
ftance.  Their  obliquity  is  fuch,  that  the  right  bag 
is  wideft,  and  adheres  to  the  middle  of  the  fternum, 
but  as  it  defcends  it  inclines  to  the  left  fide,  and 
comes  from  the  very  margin  of  the  fternum.  The 
left  bag  defcends  not  from  the  fternum,  but  from 
the  cartilages  of  the  ribs.  The  inner  and  oppofite 
fides  of  each  bag,  form  what  anatomifts  call  the 
mediaftinum.  Tliefe  bags  have  no  communication 
whatever,  and  the  right  may  be  opened  and  its 
luna;  dcliroycd,  without  irdurins;  the  left.  But  the 

membrane 


Chap.  IV, 


HEART* 


33 

membrane  which  forms  them,  is  fimple,  denfe,  ex* 
ternally  furrounded  by  ceUular  fubftance,  is  called 
the  pleura,  is  harder  than  the  peritonaeum  efpe- 
ciaUy  towards  the  back^  fofter  anteriorly,  and  is 
naturally  infenfible.  The  cavity  of  the  mediafti- 
num,  or  interval  between  the  right  and  left  bags, 
broadeft  above,  but  alfo  confiderable  below,  con* 
tains  the  thymus,  conglobate  glands,  fat,  velfels, 
and  in  fome  difeafes,  pus. 

Lxxviii.  Below,  the  fame  bags  diverging,  re- 
cede from  each  other,  and  leave  a cavity  central 
in  all  its  dimenlions,  which  feparates  them.  This 
cavity  is  the  pericardium.  But  the  bags  of  the 
pleura,  defcending  at  the  lides  of  the  pericardium, 
and  before  and  behind  it,  terminate  hnally,  about 
the  fifth  or  fixth  rib,  upon  the  diaphragm,  and  on 
it  have  their  bafis,  which  is  truncated  obliquely, 
fo  that  anteriorly  it  is  fliort,  but  pofteriorly  de- 
fcends  farther,  and  is  arched  upwards*  Within 
thefe  bags  are  the  lungs.  Pofteriorly,  thefe  bags 
are  more  tender,  contiguous  and  feparated  in  the 
fame  manner  by  cellular  fubftance,  which  termi* 
nates  on  the  pericardium,  and  includes,  in  fome 
meafure,  the  aorta,  but  more  evidently  the  trachea 
and  cefophagus*  This  is  the  pofterior  mediaftinum. 
Triangular  productions  of  each  lamina  of  the  me- 
diaftinum form  the  ligaments  of  the  lungs,  one  on 
each  fide. 

Lxxix.  The  pericardium,  or  third  bag,  which  is 
loofely  furrounded,  firft  by  cellular  fubftarice,  and 
then  on  aU  fides  by  the  contiguous  pleura,  as  an  ex- 
terior lamina,  touches  the  fternum  by  a very  fmall 
part  indeed ; fince  the  lungs  when  diftended,  cover 
the  heart  almoft  wholly  before,  and  interpofe 
themfelves  betwixt  the  fternum,  and  pericardium 
below ; and  the  mediaftinum,  by  gradually  diverg- 
ing towards  the  left  fide,  has  an  interval,  narrow 
indeed,  under  the  lower  end  of  the  thymus,  to  each 
fide  of  which,  the  lungs  extend : but  this  fituation 
D is 


HEART. 


Chap.  IV. 


34 

is  dircurbed,  iinlefs  you  are  careful  in  tlie  manner 
of  opening  the  thorax.  The  pericardium  has  a 
broad,  fomewhat  round  bafis,  adhering  to  the  ten- 
dinous, and  by  a fmaUer  part  on  the  left  fide,  about 
the  fifth  or  fixth  rib,  to  the  fielliy  part  of  the  dia- 
phragan  ; in  young  fubjects  by  loofe,  but  in  adults 
by  very  firm,  cellular  fubftance.  Towards  the  right 
it  is  broader,  and  towards  the  left  it  grows  imalier. 
It  is  fomewhat  larger  than  the  heart,  that  it  may 
move  freely  in  it.  It  never  certainly  was  wanting. 

Lxxx.  Upwards,  the  pericardium  grows  gradu- 
ally narrower,  ending  above  the  heart  in  an  obtufe 
conical  appendix,  which  adheres  to  the  coats  of  the 
large  blood-veffels  almoft  to  the  upper  edge  of  the 
fternum  ■,  iirfi;  to  the  inferior  branch  of  the  right 
fuperior  pulmonary  vein  ; then  to  the  vena  cava ; 
after  that  to  the  aorta,  on  its  acceffion  to  wliich  it 
is  higheft ; then  dovenwards  to  the  fame  velfel,  and 
the  ducfus  arteriofus  ; hence  to  the  left  branch  of 
the  pulm.onary  artery,  and  at  laft  to  both  branches 
of  the  left  fuperior  pulmonary  vein.  On  the  back 
part  it  is  again  attached  to  the  right  pulmonaiy 
vein  ; then  to  the  left  fmus,  to  both  left  pulmonary 
veins,  and  to  the  auricle  of  the  fame  fide  ; then  a 
long  way  from  the  pulmonary  vein  to  the  inferior 
cava,  then  to  the  feptum  of  the  fmufes,  then  to  the 
inferior  cava.  Befides,  it  adheres  to  the  pulmonary 
artery,  its  right  branch,  and  the  aorta  below  the 
origin  of  its  great  branches,  furrounding  each  ar- 
tery with  a cylindrical  production,  fo  that  it  ap- 
pears like  a kind  of  partition  between  every  two 
neighbouring  veiTels.  Thus  alfo  it  contains  the 
vena  cava  fuperior  in  a ring ; and  the  anterior  and 
pofterior  cavities  of  the  pericardium  are  loofely 
continued  between  that  vein  and  the  aorta.  In 
like  manner  it  furrounds  the  inferior  cava.  But 
this  fireath,  by  which  the  velTels  are  furrounded, 
preferves  its  nature  only  for  a flrort  fpace,  and 
immediately  returns  to  the  lieart  with  thofe  large 

vellels 


Chap.  IV. 


HEART. 


35 

veffels  which  it  there  ferves  as  an  external  coat. 
But  it  fends  cellular  fubilance  like  a Iheath,  along 
with  the  great  arteries  and  veins,  to  the  lungs. 

Lxxxi.  The  pericardium  has  its  arteries  either 
from  thofe  of  the  thymus,  from  thofe  which  ac- 
company the  phrenic  nerve  above  and  below,  from 
the  larger  phrenic  arteries,  from  the  mediaftinal 
branches  of  the  mammary,  from  the  bronchial, oefo- 
phageal  and  polterior  m.ediaftinal  arteries,  or  from 
the  coronaries  which  inofculate  with  the  bronchiais 
and  others.  The  trunks  of  the  veins  are  analogous, 
but  with  more  evident  anafcomofes  between  thofe 
of  the  right  and  left  fides.  The  nerves  are  from 
the  fuperficial  cardiacs. 

Lxxxii.  The  membrane  which  properly  confd- 
tutes  the  pericardium,  is  ftrong,  white,  compact, 
more  robuft  than  the  aorta  itfelf,  and  through  its 
fubftance  the  nerves  of  the  heart  and  forne  final! 
vefl'els  defcend.  The  furrounding  cellular  lub- 
flance  makes  its  outer  furface  fomewhat  rough, 
while  internally,  where  it  is  in  contacl  with  the 
heart,  it  is  very  fmooth,  and  moillened  on  aU  fides 
by  a watery  vapour.  This  halitus,  which  we  have 
always  obferved  in  the  living  animal,  conhitutes 
the  water  of  the  pericardium,  fmall  in  quantity, 
but  always  prefent,  limpid,  or  tinged  with  yellow 
or  red,  fomewhat  vifcid,  erroneoully  denied  by 
fome ; and  in  fome  difeafes  immenfely  increafecl. 
The  nature  of  this  fluid  is  lymphatic,  becaufe  it 
thickens  into  a gelly  by  heat,  and  in  difeafes,  mix- 
ed with  the  mucus  Vv^hich  every  where  exudes  from 
the  heart  and  its  pericardium,  it  concretes  into 
villi  and  cellular  fubftance.  This  liquor  is  fecreted, 
without  any  glands  or  viftble  pores,  from  the  ex- 
haling arteries  of  the  heart,  auricles  and  pericar- 
dium ; as  may  be  proved  by  the  tranfudation  of 
water  or  ftze  injected  into  the  large  arteries. 

i.xxxiii.  The  ufe  of  the  pericardium  is  to  con- 
tain this  vapour,  and  the  heart,  fo  that  it  may  have 
D 2 a fixed 


HEART. 


Chap.  IV, 


3^ 

a fixed  point,  to  which,  when  in  motion,  as  to  a 
fulcrum,  it  may  draw  its  fibres,  without  ftretching 
the  large  veffels,  and  that  it  may  not  fhift,  pendu- 
lous, on  changing  the  pofition  of  the  body.  For 
thefe  reafons,  we  find  it  in  all  animals  that  have  a 
true  heart.  A watery  vapour  bedews  the  very 
hot  and  very  rapidly  moved  heart.  It  prevents 
fricfion,  and  its  cohefion  with  the  pericardium  ; 
for,  when  this  vapour  is  dried  up,  the  pericardium 
adheres  to  the  heart,  either  in  fome  particular 
place,  or  over  its  whole  furface,  fo  that  it  may 
feem  to  be  wanting. 

Lxxxiv.  Nature  has  g-Iven  to  moft  animals,  and 
even  to  many  infefts  and  vermes,  a heart ; flie  has 
denied  it  to  others,  and  indeed  to  the  moft  fimple 
animals,  beins;  thofe  which  are  irritable  over  their 
whole  body,hov/ever  large,as  the  holothuria  hydra. 

Lxxxv.  The  veins  which  carry  back  the  blood 
from  the  whole  body  to  the  heart,  if  we  except 
thoie  of  the  lungs,  are  two.  Anatomifrs  call  them 
the  cava,  but  they  either  never  form  one  finglc 
trunk,  or  for  a very  fliort  fpace.  Of  thefe  large  veins, 
the  inferior  is  the  largeft,  and  in  man  afcends  in  the 
right  fide  direftly  above  the  diaphragm.  Towards 
the  right  it  is  fomewhat  gibbous,  that  it  may  meet 
the  fuperior  cava,  and  pofteriorly  it  forms  the 
feptum,  which  interv'^enes  between  the  right  and 
left  finufes.  But  the  left  fide  of  the  vein  unites 
with  the  right  auricle,  whofe  fibres  are  continuous 
with  thofe  of  the  cava.  The  fame  is  true  of  the 
fuperior  cava. 

Lxxxvi.  A cavity  is  thus  produced,  whofe  right 
fide  is  free,  convex,  and  compofed  by  the  union  of 
the  tvm  venae  cavae,  and  which  is  filled  vath  flefhy 
fibres,  varioufly  intersvoven  between  the  two  limplc 
membranes.  The  fam.e  cavity,  at  its  anterior  and 
left  partds  perpendicularly  oblong,  and  almoft  oval ; 
anteriorly  it  is  dilated ; and,  laftly,  upwards,  it  has 
an  acute  blind  termination,  detached  from  the  heart, 

and 


Chap.  IV. 


HEART. 


37 

and  refting  upon  the  aorta.  This  cavity  evei'y 
where  between  the  external  membrane  of  the  heart 
and  its  own  very  thin  internal  membrane,  has  very 
copious  fibres,  fiefhy,  detached,  almoft  parallel,  yet 
obliquely  interfecting  each  other,  v/hich  arifing 
from  the  right  fide  of  the  whole  cavity,  and  from 
the  left,  are  extended  round  its  anterior  femicylin- 
der,  in  the  manner  of  parallel  arches.  Very  minute 
oblique  fibres  conned:  thefe  mufcular  arches.  This 
anterior  and  ftringy  part  is  called  the  auricle,  but 
the  right  and  pofterior  portion  is  called  the  finus, 
which  is  fmooth  along  the  feptum  of  the  auricles, 
and  between  the  anulus  ovalis  and  mouth  of  the 
heart  to  the  left  of  the  vena  cava.  In  the  auricle 
are  three  confiderable  mufcles,  the  anterior,  pofte- 
rior, and  inferior. 

Lxxxvii.  Towards  the  left  of  the  feptum,  which 
divides  the  two  auricles,  almoft  in  the  middle  be- 
tween the  two  venas  cavae,  there  is  a depreffion,  as 
if  imprinted,  deeper  above,  lefs  deep  below,  in 
which  the  feptum  is  exceedingly  thin.  I fliall  call 
it  the  fofla  ovalis.  A fleftiy  column  bounds  it  on 
each  fide,  by  the  junction  of  which,  is  formed  an 
arch,  convex  upwards,  whofe  ftefliy  fibres  are 
ftretched  around  in  the  form  of  arches,  while  their 
lower  and  thinner  roots  are  turned  backwards  to- 
wards each  other.  This  I call  the  anulus  ovalis  ; 
others,  the  ifthmus. 

Lxxxviii.  Where  the  afcending  cava  opens  in- 
to the  right  auricle,  froih  the  left  tumid  column  of 
the  foramen  ovale  arifes  a membrane  of  a crefcent 
fliape,  naturally  entire,  but  from  its  thinnefs  fome- 
times  reticular  in  adults ; which  being  extended 
round  the  lower  edge  of  the  auricle,  always  grow- 
ing thinner  as  it  returns  incurvated  to  the  right, 
circumfcribes  almoft  half  the  circumference  of  the 
auricle,  and  feparates  it  from  the  vena  cava,  in  the 
manner  of  a feptum,  It  is  called  the  valve  of  Eu- 

ftadiius. 


HEART. 


38 


Chap.  IV, 


ftacliius.  The  foianien  ovale  we  fliall  defcribe 
hereafter. 

Lxxxix,  Into  this  linus  and  auricle,  which,  how- 
ever, compofe  but  one  porch  of  the  heart,  the 
blood  of  the  two  venae  cavae  is  impelled  by  the 
niufcular  power  which  refides  in  each  of  thefe 
veins  ; for  as  far  as  they  lie  within  the  breaft,  they 
are  endov'-ed  vAth  ftrong  and  irritable  mufcular 
fibres,  by  whofe  contraction  the  blood  is  driven 
into  the  neiehbourins:  auricle. 

O ^ 

xc.  In  like  manner  the  auricle,  when  irritated, 
contracts  in  every  dimenfion.  Firft,  by  the  con- 
Itriction  of  tlie  mufcular  lacerti  of  the  auricle,  its 
anterior  femicylinder  is  reduced  to  a plane,  while, 
by  contracting  at  the  anterior  extremity  or  begin- 
ning of  the  heart,  and  at  the  poflerior,  or  finus, 
they  draw  the  middle  of  the  arch  backwards.  Then 
the  appendix  of  the  auricle  defeends  and  contracts 
tranfverfely,  while  the  lower  part  afeends  ; and 
thus  the  auricle  is  lliortened.  Laftly,  the  left  hde 
approaches  evidently  to  the  right,  and  the  right 
fornewhat  to  the  left,  and  thus  the  auricle  is  ren- 
dered narrower.  Into'  the  mouth  of  the  heart, 
now  free,  the  blood  is  impelled  like  a wedge 
through  the  aperture  cf  the  valves,  fo  that  the  flat 
fides  of  the  valves  in  the  right  ventricle  are  every 
where  applied  to  tlie  fidcs  of  the  heart.  The  blood 
is  now  hindered  from  returning  again  into  the 
loveer  ca\  a,  cn  the  ccntraclion  cf  the  aui'iclc,  bqth 
by  the  reliftance  of  the  fucceeding  blood  from  the 
abdomen,  and  by  the  Euftachian  valve  ; and  from 
returning  upwards  it  is  prevented,  both  by  the 
iubfequent  blood  and  its  gravity.  It  is  driven 
back,  however,  both  ways,  if  there  be  any  obflacle 
in  the  lun2;s. 

xci.  The  heart  itfelf,  in  feme  meafure,  refembles 
half  a cone.  The  fecdon,  palling  through  the  axis 
of  the  cone,  and  dhdding  it,  is  almofl  triangular, 
]3ut  with  an  obtufe  nearly  bifid  point,  and  flattened 

tp 


Chap.  IV. 


HEART. 


39 

to  the  form  of  the  diaphragm,  refls  upon,  and  is 
fuilained  by  it.  But  the  convex  furface  of  the  cone 
is  fo  inclined  within  the  pericardium,  under  the 
great  blood-veffels,  that  its  thicker  lemicircular 
cavity  lies  in  the  fuperior  and  left  fide,  the  obtufe 
margin  of  the  moderns  *,  while  below,  and  anteri- 
orly, it  is  extenuated  into  a kind  of  edge,  or  the 
acute  margin.  The  point  is  turned  a little  forwards. 
This  is  the  fituation  in  man  ; for,  in  brutes,  the 
heart  being  almoft  parallel  to  the  larger  axis  of  the 
thorax,  its  apex  only  touches  the  diaphragm. 

xcii.  The  whole  heart  is  hollow ; and  continuous 
with  the  right  auricle  and  finus,  as  they  are  called, 
it  has  its  properly  anterior,  though  formerly  called 
its  right  ventricle,  broad,  refembling  the  fourth 
part  of  a cone,  not  fo  long  as  the  left  ventricle^  but 
larger,  and  terminating  in  the  fiiorter  tip  of  the 
bifurcated  apex.  The  mouth  of  this  ventricle,  where 
it  opens  into  the  auricle,  is  elliptical,  and  termina- 
ted by  a white  margin,  not  fo  much  tendinous,  as 
callous  and  glutinous,  on  which  a ftratum  of  flelhy 
fib  res  refts,  and  externally  fome  fat. 

xciii.  From  this  margin  is  extended,  within  the 
heart,  a membranous  ring,  formed  by  a reduplica- 
tion of  the  internal  membrane  of  the  auricle,  float- 
ing within  the  auricle  and  fo  far  entire.  But  this 
fame  ring,  in  that  part  which  hangs  within  the 
ventricle,  is  divided  into  three  unequal  trapezic 
portions,  in  fuch  a manner,  that  you  may,  in  ibme 
meafure,  give  them  the  name  of  valves ; and  reckon 
three  of  them.  They  are,  however,  continued 
parts  of  one  ring,  only  broader  here.  Thefe  were, 
by  the  ancients,  named  triglochines. 

xciv.  The  furface  of  thefe  valves  which  lies  next 
to  the  fides  of  the  heart  is  flrengtliened  by  tendi- 
nous fibres, which, m.eeting  together  in  their  courfc, 
are  inferted  by  fome  very  ftrong  cords,  lying  in 
rows  on  each  other,  partly  into  the  fides  of  the 
heart,  and  partly  into  papillary  or  cylindrical 

mufcleSs 


40 


HEART. 


Chap.  IV. 


mufcles,  ariling  towards  the  right  from  the  left 
part  of  the  right  ventricle,  bifid,  trifid,  or  even 
branchy.  The  largeft  is  that  which  anfwers  to 
the  biggeft  of  the  valves,  which  is  both  the  upr 
permoit  and  that  which  anfwers  to  the  adjacent 
mouth  of  the  pulmonary  artery.  The  middle 
valve  lies  next  the  feptum  of  the  heart.  The 
leaft  of  them  is  the  loweft,  and  moft  anterior  in 
the  acute  margin, 

xcv.  The  uie  of  this  valve  is  evident;  for,  on  the 
contraftion  of  the  right  auricle  (xc.)  the  blood 
contained  in  the  right  porch  of  the  heart  being 
forced  into  the  open  extremity  of  the  auricle,  that 
is,  the  mouth  of  the  heart,  feparates,  in  the  manner 
of  a wedge,  the  pendulous  portions  of  the  ring,  call- 
ed valves,  and  prefles  them  to  the  fidcs  of  the  heart. 
Thus  the  right  ventricle  of  the  heart  is  filled,  while 
the  uppermoft  valve  (xciv.)  fliuts  the  pulmonary 
artery,  left  the  blood,  with  the  weak  impulfe  of  the 
auricle, fhould  enter  that  artery ; but  that  being  firft 
received  into  the  heart,  by  its  flrong  contraction  it 
may  be  more  powerfully  expelled  into  the  artery. 

xcvi.  Ey  this  blood,  copious,  warm  and  hea^y, 
the  fenfible  flelli  of  the  heart  is  irritated  and  ex- 
cited to  contraction  : for  that  the  heart,  on  being 
irritated,  will  contract  itfelf  in  a moribund,  or  re- 
cently dead  animal,  is  proved  by  the  injection  of 
water,  and  inllation  of  air,  renewing  the  motions 
of  a heart  after  having  become  quiefcent. 

xcvn.  The  motion  of  the  heart  is  performed  by 
mufcuiar  fibres  ; the  origins  of  which,  in  general, 
are  from  rings  formed  of  firm  cellular  fubftance, 
iuch  as  I have  defcribed  in  xcii.  and  with  which 
all  the  large  blood-vefiels  cf  the  heart  are  furround- 
ed.  The  fibres  from  thence  defcend  gradually  in 
an  oblique  courfe  towards  the  left  fide,  and  to  the 
apex,  in  many  itrata,  fometimes  a little  decutfating, 
of  which  the  m.iddle  ones  are  more  tranfverfe,  the 
outer  molt  and  innermolt  more  direcT.  In  the  flat  fide 

of 


Chap.  IV. 


HEART. 


41 


of  the  heart  (xci.)  the  fibres  are  few ; and  fo  thin, 
that  next  to  the  fat,  the  cavity  is  found  aimoft  un- 
covered, The  ventricle,  which  is  denominated  the 
left,  is  furrounded  by  very  firm  fibres  ; which,  in 
the  feptum,  flightly  decuffating,  are  interwoven 
with  thofe  of  the  right  fide.  Many  of  thefe  fibres, 
in  their  progrefs  towards  the  apex,defcend  into  the 
cavities  of  the  heart,  and  being  interwoven,  even 
repeatedly,  in  the  manner  of  a net,  intercept  mefities 
hid  amongft  the  mmfcular  lacerti,  and  form  the 
flelhy  columns  mentioned  at  xciv.  Others,  at  the 
apex,  convoluted  in  a fpiral  direction,  terminate  the 
bifid  ventricles  with  a firm  mafs.  A very  thin  and 
fmooth  membrane  covers  both  the  external  and 
internal  furface  of  thefe  fibres  ; but  the  external 
membrane,  efpeciaily  about  the  coronary  veflels, 
contains  much  fat.  I have  not  been  able  to  obferve 
with  fufficient  precifion,  any  thing  further  in  the 
human  heart ; becaufe  it  is  the  peculiar  property 
of  the  fibres  of  the  heart  to  be  joined  by  branchy 
appendices,  fo  that  they  cannot  be  feparated  any 
where  without  laceration. 

xcviii.  But  eminent  anatomifi;s,whofe  ingenuity 
and  candour  I refpect,  have  publilhed  the  evolution 
and  defcription  of  thofe  fibres.  They  allege,  that 
the  external  fibres  of  the  heart  defcend  to  the  apex, 
common  to  both  ventricles  ; that  in  their  couffe, 
fome  infert  themfelves  into  the  feptum, while  others 
perforate  the  left  ventricle  near  the  point,  and  be- 
ing reflected,  return  along  the  inner  furface  of  that 
ventricle,  to  the  bafis,  in  a contrary  direction.  But 
there  are  other  middle  fibres,  betwixt  the  aforefaid 
inner  and  outermofi:  ones,  which  being  varioufly  in- 
clined, and  towards  the  bafis  principally  traniverfe, 
form  the  feptum.  Other  anatomifts  have  given  fig- 
ures and  defcriptions  of  many  layers  of  fibres,  of 
which  the  external  and  internal  have  contrary  di- 
rections, and  the  intermediate  are  tranfverfe.  As 
thefe  do  not  differ  very  much  from  my  own  obfer- 

yations, 


43 


HEART. 


Chap.  IV. 


vations,  I by  no  means  undertake  to  deny  them,  al- 
though I have  never  feen  this  difpofition  fufiiciently 
manifeft,  and  am  acquainted  mth  great  anatomifts 
who  have  not  been  more  fuccefsful  than  myfelf. 

xcix.  Thefe  fibres  of  the  heart,  like  other  mufcles, 
are  furaiflied  with  nerves  of  their  own,  numerous 
and  of  various  origin.  The  firft  and  uppermoft,  on 
the  left  fide,  come  from  the  uppermoft  cervical 
ganglion  of  the  intercoflal  nen^e.  With  it  are  join- 
ed others  from  the  pharyngeal  plexus,  formed  of 
the  foft  nerves,  proceeding  from  that  ganglion,  and 
from  the  glolfo-pharyngeal  nerve;  others  are  added 
from  the  trunk  of  the  intercoftal  nerve  ; others 
from  the  middle  ganglion  feated  on  the  ftraight 
mufcle  about  the  paflage  of  the  thyroid  artciy, 
which  has  branches  both  from  tliat  uppermoft 
nerve,  and  from  the  trunk  of  the  intercoftal  and 
phrenic  nerves  ; and  others  from  the  recurrent 
neiwe  of  the  eighth  pair.  The  nerves  of  the  heart, 
originating  from  thefe  fources,  woven  togetlier  into 
a plexus,  partly  before  the  aorta,  on  which  thofe, 
hereafter  mentioned,  are  alfo  added  ; and  partly 
after  forming  feveral  fmall  plexufes  between  the 
trachea  and  the  large  arteries  iffuing  from  the 
heart,  form  one  or  more  plexufes,  in  which  the 
neiwes  of  the  right  and  left  lide  arc  united,  though 
fometimes  they  remain  diftinct.  From  this  plexus, 
or  plexufes,  fome  branches  pafs  between  the  aorta 
and  pulmonary’  artery''  to  the  right  artery  of  tlie 
heart ; others  crofs  the  pulmonary  artery,  and  go 
between  it  and  the  auricle  of  the  i'ame  fide  to  tne 
left  coronary  artery  ; others  behind  the  pulmonary 
arrteiy  to  the  fame  coronary’ ; and  others,  again,  dc- 
feend  very  deeply  behind  the  right  pulmonary  ar- 
tery to  tlie  left  finus  and  fiat  furface  of  the  heart. 
To  the  plexus,  above  deferibed,  other  large  nerves 
are  added  from  the  fifth  and  lower  cervicals,  and 
idmetimes  from  the  phrenic  nerve,  and  from  tlie 
iewefi  cervical  ganglion  of  the  inter: ofial,  with 


Chap.  IV. 


HEART. 


43 

which  are  united  very  large  roots  from  the  loweil 
cervical  nerves.  Thefe,  larger,  very  foft,  and  tranf- 
vcTic,  are  partly  mixed  with  the  former  plexus, 
and  partly  go  to  the  lungs.  Lafdy,  fome  fmaii 
branches,  uncertain  as  to  courfe  and  number,  come 
from  the  recurrent  and  eighth  pair  of  nerves,  vari- 
ouhy  inofculated  with  the  intercoilals,  and  blended 
with  the  eighth  pair.  Thofe  nerves,  which  fome 
eminent  anatomifts  have  leen  afcending  through 
the  foramen  of  the  vena  cava,  from  the  great  ab^ 
domirial  plexus,  to  the  heart,  I have  never  been 
able  to  find  ; althousrh  it  is  eafy  to  difeover  the  di- 
aphragmatics  arifing  in  that  place,of  which,  though 
having  ganglions  peculiar  to  themfelves,  thofe 
anatomifts  make  no  mention. 

c.  That  thefe  nerves  conduce  povrerfully  to  the 
' motion  of  the  heart,  is  the  opinion  of  eminent  anat- 
omifts, from  a confideration  of  the  common  nature 
of  mufcles ; and  from  the  increafe  of  motion  in  the 
heart,  on  irritating  the  eighth  pair  of  nerves,  or 
brain,  or  fpinal  marrow , ?,nd  from  the  languor  that 
enfues  upon  tying  thofe  nerves,  for  the  moft  part 
either  immediately  fatal,  or  certainly  within  a few 
days,  although  it  is  poflible  to  tie  only  a few  of 
them  , for  the  intercoftal,  and  ftill  more  thofe  from 
the  uppermoft  thoracic  garnglion,  cannot  be  tied. 

ci.  But  that  fomethins:  elfe  is  comnrehended  in 
the  caufe,  appears  from  the  motion  of  the  heart  re- 
maining undifturbed  in  the  living  animal,  after  ex- 
ceilive  irritation  of  the  nerves  ; from  its  continuing 
after  the  moft  extenfive  wounds  of  the  head,  and 
even  of  the  cerebellum  and  medulla  fpinalis,  nay, 
even  in  the  heart, v/hen  torn  out  of  thebreaft,  chiefly 
in  thofe  animals  in  which  the  lungs,  being  pervious, 
make  no  refiftance  to  the  powers  of  the  heart  ; 
moreover,  from  the  lively  aftion  of  the  heart  in  tlie 
foetus  before  the  brain  is  completed,  and  in  anim.als 
wanting  the  head.  And  all  our  experiments  agree, 
that  the  quiefeent  heart,  in  moribund,  and  finally 


44 


HEART. 


Chap.  IV. 


in  dead  animals, when  irritated  by  warmth,  vapour, 
cold,  poifon,  and  efpecially  by  a current  of  air,  wa- 
tery liquors,  wax,  or  blood,  or  by  an  electric  fpark, 
is  immediately  contracted,  and  all  its  fibres  excited 
to  quick  and  violent  motion,  fometimes  general 
throughout  the  whole  heart,  and  fometimes  con- 
fined to  one  part  of  it. 

cii.  Thus,  then,  there  relldes  in  the  fibres  of  the 
heart  an  impatience  of  ftimulus  ; fo  that  in  various 
places  of  the  vifcus,  even  when  almoft  dead, 
wrinkles,  and  motions,  appear  to  be  propagated 
through  it,  as  if  from  radiating  points  : again,  the 
heart,  when  torn  out  and  cold,  on  being  pricked, 
inflated,  or  irritated,  contracts  itfelf  *,  and  the  fi- 
bres of  a dilTecled  heart,  corrugate  themfeives  orbi- 
cularly, when  it  is  no  longer  fupplied  either  with 
nerve  or  artery.  This  irritability  exifts  in  a great- 
er degree,  and  remains  longer  in  the  heart  than  in. 
any  other  part  of  the  body ; fo  that,  by  flimulating 
it,  the  motion  of  the  heart  may  be  renewed  at  a 
time  when  that  or  no  other  mufcle  can.  I'hc  heart 
of  the  foetus  is  more  irritable,  as  well  as  larger,  in 
proportion,  than  in  adults  ; and  very  tenacious  of 
its  mobility,  even  in  the  cold.  This  mobility  is  in- 
herent in  the  heart,  and  is  neither  derived  from  the 
brain,  nor  the  foul ; fince  it  remains  in  the  dead 
animal,  and  in  the  heart  when  torn  out  of  the 
breafl  ; and  cannot  be  accelerated  or  retarded  by 
volition. 

CHI.  The  heart,  therefore,  when  ftimulatcd  by 
the  venous  blood  thrown  into  it,  contracls.  Tliis 
convulilve  contraction  is  made  with  great  celerity, 
and  a manifck  corrugation  of  the  fibres ; and  the 
whole  heart  becomes  fhorter,  thicker,  and  harder. 
Idle  left  ventricle  is  drawn  fomewhat  towards  the 
feptum  of  the  heart,  and  the  right  one  more  fo. 
Ike  bafe  aifo  advances  towards  the  apex  ; but  tlie 
apex  more  evidently  towards  the  bafis.  This  I 
have  Qften  obferved  with  the  greatefl  certa.i]'ty  in 


Chap.  IV. 


HEART. 


45 

dilTecliing  living  animals ; fo  that  thofe  learned 
gentlemen  mull  have  been  fome  how  deceived, who 
have  afferted,  that  the  heart  is  elongated  during 
its  contraftion.  But  the  heart  does  not  feem  to 
turn  pale  in  warm  blooded  animals.  Even  the  fep- 
turn  of  the  heart  is  rendered  Ihorter,  and  draws 
itfelf  towards  the  balls.  By  this  adion,  the  flelhy 
parts  of  the  heart  fwell  inwardly,  and  comprefs  the 
blood,  as  they  do  the  finger  when  introduced  udth- 
in  it.  But  that  the  heart  is  completely  enough 
emptied,  appears  both  from  the  event ; from  the 
-evident  palenefs  in  animals  whofe  heart  is  white, 
as  frogs  and  chickens ; and  from  the  uneven  inter- 
nal furface,  which  has  everywhere  eminences  and 
correfpondent  hollows,  and  thick  reticular  columns 
interrupted  by  furrows.  Befides,  the  apex  of  the 
heart,  being  turned  a little  forwards,  like  the  radius 
of  a circle,  and  being,  moreover,  driven  forwards 
by  the  left  venal  finus,  which  is  at  that  time,  par- 
ticularly filled,  ftrilces  againfi:  that  part  of  the  peri- 
cardium next  the  thorax,  about  the  fifth  or  fixth 
rib.  In  ftrong  exfpiration,  it  is  carried  with  con- 
fiderable  force  upwards  and  forwards.  Both  fads 
are  proved  by  experiment. 

CIV.  The  blood,  prefled  by  the  contradied  heart, 
(cm.)  endeavours  to  efcape  in  all  diredrions  ; but 
fince  the  contraflion  begnin  in  the  fides  of  the  heart 
drives  the  blood  towards  the  axis  of  the  ventricle, 
that  part  of  the  blood  which  lay  betwixt  the  ve- 
nous ring  (xciii.)  and  fides  of  the  heart,  carries 
the  ring  before  it,  and  extends  its  loofe  extremities 
inwards.  As  this  happens  to  the  whole. circum- 
ference of  the  ring,  it  becomes  extended,  throws 
back  a part  of  that  blood  which  had  defeended  into 
the  cone  of  the  open  valve,  into  the  right  auricle  5 
and,  laftly,  fhuts  up  the  venous  orifice  more  clofely 
as  the  heart  contrails  more  firongiy,  and  without 
doubt  would  force  the  tricufpid  valves,  as  they  are 
called,  invertedly  into  the  auricle,  if  the  papillary 
mufcles  (xciv.)  did  not  keep  down  their  edges,  and 


HEART. 


Chap.  IV. 


46 


by  their  contraction,  which  is  the  fame  with  that 
of  the  heart,  retain  them  firmly  in  thatpolition  in 
vchich  the  chords  connected  with  the  valve  are  ex- 
tended, without  being  injured. 

cv.  But  the  fame  effort  of  the  blood  opens  to  it 
another  paflage.  Whilft  the  right  larger  valve 
(xciv.)  approaches  towards  the  axis  of  the  heart, 
it  leaves  the  mouth  of  the  pulmonary  artery,  which 
it  clofed,  and  the  blood  opens  it,  preffes  the  valves 
placed  in  the  artery  clofe  to  its  fides,  and  ruflies 
into  the  artery. 

cvi.  From  the  upper  part  of  thepofterior,  or,  as 
it  is  caUed,  the  right  ventricle,  a paffage  leads  into 
the  artery,  received  as  it  were  between  producfions 
of  the  fleili  of  the  heart,  and  ftrongly  ccnnecled  to 
the  heart  by  a cellular,  callous  ring,  from  whence 
the  artery  afcends  to  the  left  and  backwards,  and 
paffes  behind  the  arch  of  the  aorta.  The  ftrength  of 
this  artery  is  moderate,  being  much  weaker  than  the 
aorta.  From  the  inner  furface  of  the  artciy,  where 
it  is  joined  to  the  heart,  the  femilunar  valves  arife. 
Each  of  thefe  is  formed  by  a reduplication  of  the 
arterial  membrane,  extended  from  the  part  of  the 
artery  next  the  heart,  upv'ards,  in  an  obtufe  and 
tuiUcientiy  hat  arch.  On  the  whole,  they  are  par- 
abolical v/ith  a loofe  and  moveable  margin.  The 
middle  of  the  edge  is  generally  divided,  fometimes 
in  the  foetus  itfeli,  by  a fmall  callous  body,  almoft 
conical,  but  made  up  of  inclined  planes ; fo  that 
the  margin,  which  would  otherwife  have  the  lliape 
of  a crefeent,  is  now  divided  into  two  crefeents. 
Betwixt  the  two  membranes  of  the  valve,  arihng 
from  the  edge  and  hrm  root  of  the  valve,  appear 
fome  mufcular  of  tendinous  fibres, partly  tranfverfe, 
feme  of  which  even  bind  the  \ -alve  to  the  conti^fu- 

O 


ous  fide  of  the  heart,  leaving  fometimes  fpaces  be- 
twixt tiicm  in  a reticular  manner.  Other  fibres 
afeend  from  the  bafii  of  the  vaivcj  and  adliereto 


the 


HEART. 


Chap.  IV. 


47 


the  callous  corpufcle.  Thefe  draw  back  the  valve, 
and  open  it. 

evil.  Each  of  thefe  valves  wdth  the  fide  of  the  ar- 
tery at  this  part  fomewhat  enlarged,  intercept  a par- 
abolical fpace,  which  towards  the  heart  is  impervi- 
ous; but  open  upavards,as  we  obferved  of  the  valves 
in  the  veins  (xnix.)  When,  therefore,  the  blood  is 
impelled  towards  the  axis  by  the  contraction  of  the 
heart,  it  efcapes  in  the  diredion  of  that  axis ; pen- 
etrates like  a wedge,  betwixt  the  valves,  preffes 
their  loofe  membranous  edges  againft  tlie  fides  of 
the  pulmonary  artery,  and  flows  out  freely.  This 
appears  from  the  mechanifm,  from  injection,  from 
ligatures,  and  from  the  increafed  fize  of  tlie  cavities 
of  the  right  fide  of  the  heart,  when  the  lungs,  be- 
ing obftruded,  prevent  them  from  being  emptied. 

cviii.  The  blood  received  into  the  pulmonary 
artery,  circulates  through  the  lungs.  That  artery  is 
firfl  divided  into  two  branches ; of  which  the  left 
is  lefs  and  fiiorter,  and  enters  immediately  into  the 
lungs  of  that  fide:  but  the  right  branch,  larger  and 
longer,  pafles  tranfverfely  behind  the  arch  of  the 
aorta  to  its  correfponding  lungs.  From  each  of 
thefe,  by  fucceflive  fabdivifions,  very  minute  twigs 
are  produced,  of  which,  a part  exhale  a watery 
liquor  into  the  cells  of  the  lungs,  and  a part  are 
continued  into  the  veins.  That  the  blood  flows  in 
this  diredion,  is  proved  by  the  mechanifm,  by  the 
application  of  a ligature,  which,  intercepting  the 
blood  between  the  heart  and  lungs,  dilates  the  ar- 
tery ; by  polypufes  obftruding  the  mouth  of  the 
pulmonary  artery,  in  which  cafe  the  right  cavities 
of  the  heart  become  monftroufly  enlarged,  and  at 
length  burft,  while  the  left  remain  empty;  and  by 
injedion ; for  water,  fize  and  milk,  are  very  eafily 
thrown  from  the  pulmonary  artery  into  the  vein^ 
and  into  the  left  fide  of  the  heart.  But  in  frogs, 
the  anaftomofes  themfelves  of  the  arteries  with  the 
veins,  are  feen  by  means  of  the  microfeope. 


CIS. 


Heart. 


Chap.  IV. 


4S 

cix.  Nor  can  the  bloody  which  has  once  entered 
the  pulmonary  artery,  return  into  the  heart ; be- 
caufe  the  valves  (cvi.)  are  of  fuch  dimenfions, 
that,  v/hen  diftended,  they  perfectly  fliut  up  the 
opening  at  the  heart ; and  are  fo  flrong,  that  they 
are  able  to  reiift  a much  greater  force  than  the  con- 
tradtion  of  the  pulmonary  artery.  However,  fome- 
times,  from  the  great  preffure  of  the  contracted  ar- 
tery, they  grow  callous  ; or  one  of  the  membranes 
is  lacerated,  and  ofleous  matter  is  poured  in  be- 
twixt the  duplicature  of  the  valves.  For,  when  the 
blood,  by  the  contraction  of  the  artery  returns  to- 
v/ards  the  heart,  it  ftrikes  againft  the  open  mouths 
of. the  valvular  fpaces,  (cvn.)  enters  them,  expands 
thevalves,and  forces  them  towards  the  central  axis ; 
when  expanded,  they  fliut  up  the  paflagc,  fo  that 
not  even  a flit  remains,  for  that  is  prevented  by 
the  hard  corpufcles  (cvi.) 

cx.  The  pulmonary  veins,  of  which  we  fliall  fay 
more  hereafter,  are  gathered  into  branches,  and,  at 
laft,  into  four,  feldom  two,  and  ftill  more  rarely  in- 
to five  trunks  ; to  which  cuflom  has  aflixed  the  An- 
gular name  of  pulmonary  vein.  Thefe  trunks  en- 
ter the  cavity  of  the  pericardium,  from  whence  they 
receive  an  external  covering  ; and  are  then  infert* 
ed  into  the  corners  of  the  fquare,  left,  or  pofterior, 
or  as  it  is  fometimes  called  the  pulmonary  Anus. 
The  upper  veins  defeend,  the  lower  ones  afeend. 
That  thefe  veins  bring  their  blood  in  that  direction 
which  leads  to  the  Anus,  is  proved  by  ligatures, 
v/hich,  by  impeding  the  blood,  caufe  a turgefcence 
of  the  vein  betwixt  the  ligature  and  lungs. 

CXI.  This  left  Anus,  almofl;  cubical,  firmly  con- 
ftructed  of  various  fefciculi  of  fibres  rurning  be- 
tween twomembranes, has, onthe  anteriorand  right 
fide,  the  feptum,  common  to  it  and  the  right  Anus, 
(licxxvi.)  but,  at  its  anterior  and  left  edge,  it  ter- 
minates in  a conical  appendix,  notched  and  creAed 
with  proceffes,  v.'hich,  making  two  or  three  ferpen- 


Chap.  IV. 


HEART. 


49 

tine  turnings,  is  cailed  the  left  auricle,  and  with  its 
point  direfted  forwards  refts  upon  the  left  ventricle^ 
As  iji  the  right  auricle,  fome  of  its  fibres  being  bent 
into  the  form  of  an  arch,  contract  the  auricle  ; 
others,  coming  from  the  origin  of  the  appendix, 
and  inferted  into  its  apex,  deprefs  it.  This  finus, 
with  the  left  auricle,  are  fomewhat  lefs  than  the 
right  finus  and  auricle. 

cxii.  In  this  finus,  the  blood  waits  for  the  relax- 
ation of  the  heart ; at  which  time  the  nifiis  of  the 
blood  acting  againft  the  venous  valves,  and  ftronger 
than  the  adtion  of  the  finus,  remits.  Then  the  left 
finus  ftretches  itfelf  forward  acrofs  the  heart,  and  at 
the  fame  time  is  contradfed  tranfverfeiy,  and  the  ap- 
pendix becomes  evidently  fliorter  and  narrower. 
Thus  the  left  porch  impels  the  blood  into  the  left 
ventricle  of  the  heart,  in  the  fame  manner  as  the 
right  auricle  impelled  its  blood  into  the  right  ven- 
tricle (xcv.)  For,  as  in  that,  there  is  a valvular 
oval  membranous  ring,  which  has  fimilar  produc- 
tions, called  mitral  valves,  and  which  are  ufually 
reckoned  two  in  number.  Thefe  are  longer  and 
ftronger  than  thofe  of  the  right  fide.  They  have, 
in  like  manner,  ftefliy  mufcles,  one  and  one  only  to 
each,  but  much  ftronger.  And,  more  frequently 
than  in  the  valves  of  the  right  fide,  the  valves,  be- 
ing fubjedted  to  the  powerful  action  of  the  heart, 
abound  every  where  at  the  beginning  of  the  ten- 
dinous chords  with  cartilamnous  tumours. 

cxiii.  Therefore  there  comes  into  the  left  ven- 
tricle the  blood,  which  the  venae  cavas  had  fent  in- 
to the  right  auricle  (lxxxix.)  this  auricle  had 
poured  into  the  correfponding  ventricle  (xcv.)  the 
ventricle  had  propelled  into  the  pulmonary  artery 
(cv.)  and  from  it,  being  received  into  the  pulmo- 
nary veins,  \vas  conveyed  into  the  left  finus  (cx.) 
and  driven  by  it  into  the  left  ventricle  (cxii.)  This 
conftitutes  the  lefs  circulation,  aiid  was  known  to 
many  of  the  ancients  (lxii.)  It  is  proved,  by  the 
E increafed 


HEART. 


Chap.  IV« 


increafed  bulk  of  the  left  pulmonary  veins,  and  of 
the  veffels  of  the  right  cavities  of  the  heart,  on  the 
entrance  into  the  left  ventricle  being  obftruclcd. 

cxiv.  The  left,  or  pofterior,  or  upper  ventricle, 
the  firft  formed,  and  in  many  animals  the  only  one, 
occupies  that  part  of  the  half  conical  heart,  which 
v.^e  called  obtufe  (xci.)  It  is  narrovcer  than  the 
right  ventricle,  a little  longer  and  rounder,  and  its 
cavity,  on  the  whole,  hnaller.  For,  the  capacity  of 
this  ventricle  is  about  two  ounces,  while  that  of  the 
right  amounts  even  to  three.  Its  texture  internal- 
ly is  in  like  manner  reticular,  but  more  minute  ; 
and  alfo  at  the  mouth  of  the  artery  fmooth.  Its 
force  is  greater,  as  the  mufcular  flelh,  with  which  it 
is  furrounded,  is  much,  almoft  three  times,  ftronger. 
The  feptum  of  the  heart  belongs  moftly  to  the  left, 
but  fome  part  of  it  alfo  to  the  right  ventricle  : the 
whole  of  it  is  equally  reticulated  ; but  folid,  and 
does  notfuffer  any  injected  liquid  to  pals  from  one 
ventricle  to  the  other. 

cxv.  The  left  ventricle,  from  the  fame  irritable 
nature,  already  fpoken  of,  (cm.)  being  ftimulated 
by  the  blood  thrown  into  it,  contracts,  and  with 
great  energy  forces  the  blood  contained  in  it  to- 
v/ards  the  axis  and  balls,  while  the  cone  of  the  heart 
is  retracted  nearer  to  the  bafe.  And  lince  there  is 
the  fame  apparatus  of  valves,  the  blood  diltends  the 
venous  ring,  and  removes  the  right  divilion  of  the 
valve  from  the  mouth  of  the  aorta  which  it  Ihut 
up,  opens  to  itfelf  that  mouth,  preffes  thefemilunar 
valves,  there  placed,  againlt  the  fides  of  the  aorta, 
and  rullies  into  that  artery  with  a violent  impetus. 
This  is  proved  by  ocular  demonllration  in  living 
animals,  and  by  the  enlargement  of  the  left  ventri- 
cle on  obftrufting  the  palfagc  into  the  aorta. 

cxvi.  Tlie  valves  of  the  aorta  are  not  verj^  dif- 
ferent from  thofe  in  the  pulm.onary  artery.  Only  as 
the  aperture  is  here  greater,  fo  the  valves  them- 
felvcs  are  larger  and  ftronger,  and  are  fcldomer 

without 


Chap.  IV. 


HEART. 


5* 

without  thofe  callous  globule^.  The  fibres  too  of 
the  valves,  both  tranfverfe  and  afcending,  are  fome- 
what  more  confpicuous. 

cxvm  After  the  contraftion  of  the  heart,  fol- 
lows its  relaxation  or  diaftole,  in  which  it  becomes 
empty  , lax,  and  foft,  recovers  its  former  length,  the 
ventricles  dilate  from  the  feptum,  and  the  b'afis  re- 
cedes from  the  apex.  But  as  the  blood  dillending 
the  auricles,  lies  immediately  at  the  orifices  of  the 
ventricles,  it  rufhes  through  the  valvular  apertures, 
and  feparatcs  the  oppofite  fides  of  the  heart,  which 
is  thus  rendered  both  larger  and  longer.  After  the 
auricles  have  emptied  themfelves  of  the  blood  they 
contained,  they  become  in  like  manner  relaxed,  and 
their  oppofite  fides  feparate  from  each  other.  Thefe 
ventricles  are  then  filled  with  the  blood,  coliecled 
in  the  venae  cavse  and  pulmonary  veins,  by  the  con- 
traction of  the  veins  ; and,  like  the  ventricles,  are 
increafed  in  every  dimenfion,  and  even  the  pro- 
ceffes  of  the  crefied  margin  are  diftended  and  ex- 
panded. That  there  are  in  the  heart  dilating  fibres, 
is  contradicted  by  the  connection  of  its  fibres,  which, 
being  bound  together  by  intermediate  branches,  can- 
not be  feparateiy  moved,  and  by  the  difleCtions  of 
living  animals  which  Ihow  that  the  whole  heart  is 
contracted  at  the  fame  time. 

Gxviii.  But  it  mull  be  obferved,  that  thefe  mo- 
tions of  the  right  and  left  auricles,  and  of  the  right 
and  left  ventricles,  are  not  performed  in  that  fuc- 
celfion  in  which,  for  the  fake  of  method,  we  have 
defcribed  them  ; for  both  the  auricles  are  contract- 
ed, while  the  ventricles  are  relaxed,  and  the  con- 
traction of  the  auricles  precedes  the  contraction  of 
the  ventricles  ; as  we  are  convinced,  from  manifeft 
experiments  on  dying  and  on  cold  blooded  animals. 
But  both  auricles  are  filled  in  the  firit  inflant,  and 
both  of  them  are  emptied  in  the  fecond  inllant  ; 
and  both  the  ventricles  are  contracted  in  the  third 
inftant,  which  however  correfponds  to  the  firit  ; 

£ z and 


HEART. 


Chap.  IV. 


52 

and  bofth  ventricles,  being  evacuated,  are  relaxed  in 
the  fourth  inftant,  which  correfponds  to  the  fecond. 
Thofe  who  have  taught  otherwife,  have  not  taken 
fufScient  affiftance  from  experiments  on  living  ani- 
mals. That  the  auricle,  near  death,  makes  frequent 
palpitations,  before  the  ventricle  of  the  heart  per- 
forms one  contraftion,  and  that  the  motion  of  the 
right  continues  after  the  left  has  ceafed,  is  certainly 
true.  The  auricle,  with  its  Gnus,  forms  one  cavity, 
and  both  are  filled  at  one  time,  and  both  emptied 
in  the  fame  inftant, 

cxix.  But  it  may  be  alked,  why  the  heart,  with 
inceflant  motion  during  fo  many  years  as  there  are 
in  a lifetime,  during  fo  many  days  as  there  are 
in  a year,  and  when,  in  each  hour,  in  a healthy  per- 
fon,  it  contradfs  not  much  lefs  than  5000  times,  nev- 
er refts,  but  contraction  perpetually  fucceeds  re- 
pletion, and  repletion  contraction,  in  conftant  fuc- 
ceffion ; nor  is  the  heart  fatigued  or  pained  by  fo  ex- 
ceflive  an  action,  that  no  other  mufcle  could  endure 
it  even  for  a few  hours  ? To  this  queftion,  different 
profeffors  have  given  different  anfwers,  founded  up- 
on a compreffure  of  the  nerves  betwfixt  the  large 
arteries  ; upon  an  alternate  repletion  of  the  coro- 
nary arteries  and  heart,  &c. 

cxx.  But  to  me  the  fimplicity  of  nature  feems 
very  confpicuous.  When  the  auricle  is  relaxed,  it 
is  filled  by  the  mufcular  force  of  the  contiguous 
veins,  and  fo  the  heimt  in  like  manner  contracts  it- 
felf,  when  it  is  irritated  by  the  blood  conveyed 
through  the  auricle.  Therefore,  the  heart,  when  it 
has  received  the  blood,  in  confequence  of  that  irri- 
tability and  ftimulus  by  which  its  fibres  are  excit- 
ed to  adtion,  contradts,  empties  itfelf  of  the  blood, 
and,  being  freed  from  the  ftimulus,  refts  and  be- 
comes relaxed.  But  being  now  relaxed,  it  is  again 
filled  by  the  contradtion  of  the  auricle,  which  the 
fame  ftimulus  of  the  venous  blood  excites,  fince  the 
jneeffant  adlion  of  tlie  heart  and  'arteries  continual- 

Iv 

* 


HEART. 


Chap.  IV. 


53 


ly  fupply  blood  to  the  auricle.  That  this  is  the 
fact,  is  proved  from  obfervation  ; which  readily  dif- 
covers  the  fucceffion  of  repletion  and  contraction  in 
the  vein,  auricle,  ventricle,  and  artery,  in  an  exhauft- 
ed  animal ; but  more  evidently,  in  thofe  animals 
which  have  but  one  ventricle  ; as  the  tortoife,  frog, 
fnake,  fiflies  ; and  in  the  chick  in  ovo,  which,  in- 
ftead  of  a heart,  has  only  a crooked  canal.  The 
fame  is  alfo  confirmed  by  the  quiefcence  of  the 
heart,  upon  tying  the  veins  ; and  by  its  motion,  on 
removing  the  ligatures,  if  this  observation  be  cor- 
rect, but  more  certainly  on  the  injeCtion  of  air  or 
fluids  ; and  laitly,  by  the  perpetual  contraction  of 
the  heart  of  a frog,  upon  a veficle  of  air  blown  in- 
to it ; which,  it  will  force  into  the  auricle,  and  re- 
ceive, alternately,  for  many  hours.  The  left  ven- 
tricle firlt  ceafes  its  motion  ; then  the  auricle  of 
that  fide  5 then  the  right  ventricle  ; after  that,  the 
right  auricle  ; and,  lafl:  of  all,  the  pulmonary  veins, 
and  venae  cavae.  The  motion  afcribed  to  the  venae 
cavae,  proceeds  from  the  auricle,  repelling  into  both 
thefe  veins  the  bipod,  which  the  heart,  when  dead, 
does  not  receive. 

cxxi,  Nor  do  I believe  any  thing  more  required^ 
than  a continual  ftimulus  applied  to  a part  irri- 
table in  the  higheft  degree.  For,  even  in  the  arti- 
cle of  death,  the  very  coldnefs  of  the  limbs,  which 
the  warmth  of  life  has  left,  conftriCls  the  veins,  and 
drives  the  blood  to  the  heart ; at  which  time  the 
lungs,  being  impermeable  for  want  of  refpiration, 
tranfmit  no  blood  to  the  cavities  of  the  left  fide. 
On  the  other  hand,  the  heart,  thoroughly  emptied, 
remains  at  reft.  It  is,  therefore,  poflible  to  tranf- 
fer  the  prerogative  of  dying  laft  from  the  venae 
cavae  and  right  auricle,  to  the  left  auricle,  and  ven- 
tricle ; if  you  contrive  that  the  right  cavities  be 
emptied,  and  that  the  left  be  irritated  by  blood. 
But'  thofe,  who  attribute  the  quiefcence  of  the  heart 
to  the  coxnpreftion  of  its  nerves,  are  refuted  by  the 

appearances 


HEART. 


Chap.  IV. 


54 

appearances  in  thofe  auricles,  whofe  nerves  are  not 
comprelied  ; as,  for  example,  in  filhes,  and  in  the 
chick  in  ovo,  where  there  is  no  fuch  comprelhon. 
If  you  deduce  the  quiefcencc  of  heart  from  the  co- 
ronary arteries,  this  is  contrary  to  experience;  fince 
tliey  are  not  covered  by  the  valves  of  the  aorta, 
and  fince,  from  the  coronaries,  when  divided,  the 
blood  fprir.gs  to  the  greateft  height  during  the  fyf- 
tole  of  the  heart. 

cxxii.  Nor,  with  the  powers  of  the  heart,  do  I 
conicin  the  ofcillation  of  the  minute  veflels,  which 
is  refuted  by  experiments  ; nor  the  influence  of  ex- 
ternal heat ; flnce  animals  are  found  to  live  and 
thrive  in  the  coldeft  regions  of  thenorth : and  though 
the  contracfile  force  of  the  artery,  and  the  w’eight 
of  the  parts  and  of  the  atmcfphcre,  aflift  the  mo- 
tion of  the  blood  clurinQ-  the  diaftole  of  the  heart, 
the  fame  powers  refill  it  during  the  fyftole  ; fo  that 
the  blood  is  not  moved  more  eaffiy  through  the 
contractile  arteries,  than  even  through  the  rigid 
arteries  of  the  fmaller  animals. 

cxxm.  But  the  celerity  and  force  with  w hich 
the  heart  propels  the  blood,  are  varioufly  comput- 
ed. Tlie  more  modern  writers  have  calculated 
upon  the  following  pofitions.  In  determining  the 
celerity,  they  luppole  two  ounces  of  blood  to  iiTue 
out  of  the  heart  w ith  fuch  a celerity,  tliat  tliat  part 
of  the  pulfe,  called  its  fyllolc,  is  finiflred  within  the 
third  part  of  a wiiole  pulfation,  or  within  ? of  a 
minute  : and  the  area  of  the  month  of  the  aorta, 
they  have  eflimated  at  0.4187  parts  of  an  inch  : fo, 
by  dividing  3.318  inches,  the  fpace  filled  by  tv/o 
ounces  of  blood,  by  the  area  of  the  aorta  at  its  mouth, 
and  by  multiplying  by  225,  or  number  of  puifa- 
tions,  this  quotient  inches,  or  length  of  cy- 

linder of  the  aorta  which  is  filed  bv  tw  o ounces 
of  blood,  they  And  149  feet  and  tw'o-tenths  of  an 
inch  for  the  fpace  througli  whicli  the  blood  would 
run  in  a minute,  if  it  proceeded  and  paiTcd  through 


Chap.  IV. 


HEART. 


55 

the  cylindrical  aorta  with  the  fame  velocity  with 
which  it  was  expelled  from  the  heart.  But -the 
weight  of  blood  preffing  upon  the  heart,  they  have 
computed  by  the  jet  with  which  the  blood  fprings 
from  the  aorta  in  a living  animal,  being  feven  feet 
five-tenths  ; and  from  the  area  of  the  ventricle,  1 5 
inches  ; which  produce  1350  cubical  inches  of 
blood,  or  51*-  pounds  five  ounces,  w'hich  prefs  a- 
gainft  the  ventricle  of  the  contradling  heart.  The 
heart,  therefore,  propels  a weight  of  51  pounds, 
with  a velocity  by  which  it  may  run  through  149 
feet  in  a minute  ; and  this  four  thoufand  eight 
hundred  times  in  an  hour. 

cxxiv.  Although  into  thefe  calculations  many 
things  enter,  which  are  neither  eftabliilied,  nor 
perhaps  ever  to  be  cleared  up  ; although  the  mouth 
of  the  diftended  aorta  is  wider  in  a living  animal ; 
thousfh  the  menfuration  of  the  area  of  the  ventricle 
IS  uncertain,  and  the  jet  of  blood  perhaps  too  low, 
if  we  confider,  that,  in  the  living  animal,  the  blood 
iffues  with  violence  from  very  minute  arteries  ; laft- 
ly,  although  we  cannot  determine  what  part  of  an 
entire  pulfation  the  fyftole  of  the  heart  takes  up, 
variations  in  which  will,  however,  greatly  alter  the 
whole  computation  ; yet,  in  the  mean  time,  it  will 
plainly  appear,  that  the  machine  we  call  the  heart 
is  very  powerful.  This  opinion  is  fupported  by 
experiment,  which  fliews,  that  by  anatomical  injec- 
tion, it  is  very  difficult  to  fill  aU  the  red  blood- 
velfels,  and  impoffible  to  fill  all  the  fmaller  ones  ; 
while  the  heart  not  only  gradually  diftends  wntli 
blood  all  the  large,  fmall  and  minute  veffels,  but 
befides,  propels  the  blood  with  great  rapidity. 
Even  into  the  moft  minute  arteries,  the  blood  is 
driven  by  the  heart  with  fuch  force,  as  to  make  its 
alternate  m.otions  perceptible.  Likewife  in  the 
veins,  and  laftly,  in  the  fmaller  veffels,  both  in  cold 
blooded  animals,  and  in  the  chick  in  ovo,  there  is 
no  other  force  befides  that  of  the  heart,  by  which 


HEART. 


5^ 


Chap.  IV, 


the  blood  is  driven  through  thefe  veffels.  And, 
from  very  fmall  arteries,  I have  feen  the  bicod  pro- 
jected feveral  feet,  defcribing  a parabola,  whofe 
height  was  four,  and  its  extent  feven  feet  • and 
forne  abert,  they  have  feen  the  blood  thrown  out 
of  the  aorta  to  the  height  of  twelve  feet. 

exxv.  Moreover,  in  eftimating  the  force  of  the 
heart  in  living  animals,  we  muft  confider  the  pow- 
erful obliacles  it  overcomes  : v/e  muft  compute  the 
enormous  weight  of  the  whole  blood  ; for  the  en- 
tire mats,  weighing  fifty  pounds  and  upavards.  when 
at  reft,  is  eafiiy  fet  in  motion  by  the  heart  alone,  as 
in  the  inftances  of  fainting  and  refuicitaticn  from 
drovening.  We  muft,  moreover,  confider  the  great 
decreafe  of  velocity,  arifing  from  the  greater  capa- 
city of  the  branches,  which,  even  in  the  inteftines, 
it  feems  we  might  conipute  at  the  24th  or  30th 
power  of  the  root  And  yet  fluids  are  carried 
with  velocity  through  the  fmrlleft  veflels,  of  w’hich 
we  haa^e  examples  in  the  Sancloiian  perfpiration, 
w'hich  in  fubterraneous  caverns  I have  feen  rifing 
with  great  velocity,  in  the  manner  of  fmoke  ; and 
in  the  motion  of  the  blood  in  fifties,  Befidcs,  as 
friction  in  every  machine  confumes  the  greateft 
part  of  its  powers,  it  will  be  readily  conceived, 
tliat,  in  the  human  body,  in  which  a liquid,  much 
more  vifeid  than  water,  flows  in  canals  fo  narrowy 
that  they  admut  but  one  globule  at  a time,  and  not 
even  that,  without  a change  of  figure,  an  excef- 
five  retardation  muft  arife  from  friftion,  and  that 
the  power  muft  be  immenfe,  w^hich  moves  fuch  a 
mafs,  in  fpite  of  fuch  obftacles  and  diminutions  of 
its  force.  But  even  aneurifms  and  arteries  are  burft 
by  the  force  of  the  heart ; and  great  w’eights  along 
with  tlie  human  body  are  elevated  by  the  force  of 
its  f}dtole. 

exxvi.  The  blood,  when  driven  into  the  aorta, 
finds  the  mouths  of  the  two  coronary  arteries  near 
to  the  valves  of  the  artery,  but  higher  up  and  not 

covered 


HEART. 


Chap.  IV. 


57 


covered  by  them.  Into  thefe,  firft  of  all,  it  ruflies, 
and  thus  the  heart  fupplies  itfelf  with  blood.  Thefe 
arteries  are  almoll  conftantly  two,  and  arife  from 
the  heart  at  an  obtufe  angle  with  the  trunk  ; the 
right  goes  oiT  between  the  aorta  and  pulmonary 
artery,  and  the  upper  and  left  one  between  the  left 
auricle  and  the  aorta.  All  the  external  branches 
are  furrounded  with  m.uch  fat.  Their  cavity  is  not 
intercepted  with  valves  any  more  than  other  arte- 
ries. Thefe  arteries  communicate,  by  fmaU  branches, 
every  where  about  the  feptum  and  tip  of  the  heart ; 
but  they  do  not  make  a complete  ring  round  the 
heart.  They  terminate  in  two  ways. 

cxxvii.  Their  firft  termination  is  in  the  veins,  of 
which  the  branches  accompany  the  arteries,  but  the 
trunks  neceffarily  feparate.  The  left  artery  is  there- 
fore accompanied  by  the  great  coronary  vein,  which 
is  inferred  by  a large  opening,  fecured  with  a valve, 
or  feveral  little  m.embranes,  into  the  auricle  to  the 
left  of  the  Euftachian  valve.  It  is  diftributed  on 
the  bafe  of  the  left  auricle,  and  accompanies  the 
fuperficial  branches  of  the  left  artery. 

cxxviii.  The  fecond  vein  (which  you  may  make 
a part  of  the  former,  fince  they  have  both  one 
common  infertion,)  defcencls  along  upon  the  fep- 
tum of  the  heart  on  its  flat  furface ; and  may  be 
properly  called  the  median  coronary.  The  third 
tranfverfely  feeks  the  root  of  the  right  auricle,  and 
terminates  within,  or  at  leaft  very  near,  the  large 
opening  of  the  coronary  vein,  (cxxvii.)  or  in  an 
anterior  vein.  It  fupplies  that  part  of  the  right 
ventricle  which  lies  in  the  flat  fide  of  the  heart ; 
and  often  receives  the  vena  innominata,  immediate- 
ly to  be  defer ibed, 

cxxix.  There  are  ftill  fome  other  anterior  veins 
of  the  heart ; but  one,  more  confiderabie,  which 
runs  along  that  part  of  the  right  ventricle  next  to 
the  margin,  and  winding  in  an  oblique  courfe,  fome- 
tiraes  between  the  membranes,  is  inferted  into  the 

mofl: 


^8 


HEART. 


Chap.  IT. 


mofl  anterior  part  of  the  right  auricle,  and  fomc- 
times  into  the  trunk  of  the  upper  vena  cava.  Ikis 
anterior  vein  fends  off  along  the  root  of  the  right 
linus,  another  which  runs  concealed  through  the 
very  fubftance  of  the  heart,  and  beincir  asrain  infer t- 
ed.  into  the  great  coronary  vein,  completes  the  ve- 
nous- cii’cle  round  the  heart,  like  the  arterial  circle 
wdiich  fome  have  deferibed,  but  wdiich  to  me  is  un- 
known. 

ex XX.  But  there  are  a great  many  mcji'c  veins, 
uncertain  in  their  number  and  polition,  whidi,  hid 
ainong’ft  the  origins  of  the  large  veffels,  belong  to 
the  deep  fcated  and  difhcultly  acceffible  parts  of 
the  bafis  of  the  heart.  Thefe  open  by  numerous 
fmall  mouths  into  the  right  finus  and  auricle  , and, 
though  more  rarely,  into  the  left  finus.  Thus  I 
have  feen  a particular  vein,  -which,  from  a latent 
finus  in  the  flefli  of  the  right  auricle,  h-as  afeended 
towards-  the  aorta  and  pulmonary  artery,  and  in- 
ferted  itfslf  on  the  other  fide  into  the  greater  coro- 
nary vein.  I have  feen  anothev  concealed  bctv.hxt 
the  mouth  of  the  coronary  vein  and  the  -aorta,  in- 
ferted  into  the  right  finus  ; and  another  along  the 
remains  of  the  foramen  ovale,  and  feptum  of  the 
two  finufes,  inferting  itfclf  into  the  right  finus  ; 
and  others  again  belonging  to  the  venous  valves  ; 
fcefides  which,  there  are  kill  others  too  numerous 
to  deferibe.  I have  alfo  feen  a vein  arifins:  from 
the  left  finus,  inferted  into  the  vena  cava. 

cxxxr.  There  are  other  fmaller  veins,  whofe 
little  trunks  are  fliort,  and  cannot  eafily  be  traced 
by  dilTeftion.  Thefe  open  by  oblique  fliort  mouths, 
through  all  thofc  innumerable  pits  of  the  right  and 
left  ventricles,  and  into  the  feptum  of  the  heart, 
and  into  both  auricles.  Tlicfe  are  demonflrated  by 
injeciir.g  -water,  air,  or  mercury,  efpeci'aily  into  the 
coronary  arteries,  after  ha-^fing  tied  all  the  corre- 
fponding  veins ; or  even  into  the  veins  themfeh  es, 
after  having  fecured  the  infertion  of  the  Lirgeft 

truiflis. 


Chap.  IV. 


HEART. 


59 

trunks.  For,  drops  of  coloured  water,  bubbles  of 
air,  fpherules  of  mercury,  exude  through  the  whole 
extent  of  both  ventricles ; and  this,  without  any 
violence  that  can  be  fuppofed  to  have  burft  the  vef- 
fels.  The  paffage  from  the  arteries  into  the  ca^dties 
of  the  left  nde,  is,  hov^^ever,  more  difficult. 

cxxxii.  There  are  fome  who  fuppofe  that  the  co.. 
ronary  arteries  are  filled  vAth  blood,  not  by  the 
contraction  of  the  heart,  but  of  the  aorta.  Their 
opinion  is  founded  on  the  retrograde  angle  of  their 
origin,  on  their  mouths  being  covered  by  the  valves, 
and  on  the  palenefs  of  the  heart  when  contracted. 
But  the  two  lafi;  of  thcfe  are  contrary  to  fact ; and 
the  firfi;  perhaps  fomewhat  retards  or  ieffens,  but 
certainly  does  not  obftruti;  the  entrance  of  the 
blood ; for  the  injections  of  air  or  mercury  into  the 
feminal  and  biliary  veffeis  every  v/here,  demonftrate, 
that  in  a diftended  yeffel,  even  more  retrograde 
angles  do  not  prevent  fluids  from  entering  the 
branches.  Moreover,  in  the  coronary  artery,  the 
pulfe  is  fynchronous  with  the  other  arteries  in 
the  animal  body,  and  the  blood,  during  the  con- 
traction of  the  heart,  fp rings  to  a greater  height 
(cxxi.) 

cxxxiii.  Concerning  the  reflux,  there  is  lefs 
room  for  doubt : into  the  ventricles  and  auricles 
of  the  heart,  right  and  left,  but  more  into  the  lat- 
ter, all  the  blood  of  the  coronary  veffeis  is  difcharg- 
ed,  both  by  the  large  orifices,  (cxxvii.  cxxviii.- 
cxxix.)  and  by  the  ImaU  ones,  (cxxx.)  and  by 
thofe  minute  ones,  (cxxxi.)  which,  when  the  large 
veins  are  tied,  readily  tranfmit  injections.  This 
circulation  feems  to  be  completed  in  a very  fliort 
fpace  of  time,  on  account  of  the  very  great  veloci- 
ty the  blood  receives  from  the  immediate  action  of 
the  heart  itfelf.  I do  not,  however,  think  that 
it  is  effected  during  one  pulfation  ; for  the  blood- 
\^effels  of  the  heart  neither  lofe  their  colour,  nor 
are  eompletely  evacuated,  There  is  a very  free 


BLOOD, 


60- 


Chap.  V. 


paflage  from  the  arteries  of  the  heart  into  the  fat. 
What  are  the  ufes  of  the  minute  veins  r (cxxxi.) 
They  return  the  blood  of  thofe  deeply  feated  arte- 
ries, which  have  no  larger  correfponding  veins. 

. cxxxiv.  The  humours  of  the  heart,  which  are 
thinner  than  blood,  return  by  the  valvular  lymphat- 
ic veins,  which  accom.pany  the  coronary  vefl'els,  and 
afcend  towards  the  thoracic  duct  and  fubclavian 
vein ; they  are  very  rarely  to  be  feen,  but  1 have 
©bferved  them  in  brute  animals. 


CHAP.  V. 

NATURE  OF  THE  BLOOD  AND  HUMOURS  OF  THE 
HUMAN  BODY.. 

exxxv.  ^ I ' HAT  liquid  which  is  contained  in  the 
I pulfating  arteries  and  their  corre- 
fponding veins,  is  called,  by  one  comxm.on  name, 
the  blood.  When  fuperficially  viewed,  it  appears 
homogeneous,  coagulable  throughout,  and  redder 
in  proportion  as  the  animal  is  ftronger  and  fuller 
fed  j in  a weak  and  famiflied  one  it  inclines  to  a 
yellow.  Any  admixture  of  white  generally  pro- 
ceeds from  chyle.  But  experim.ents  of  various 
kinds  have  demonftrated  the  compound  nature  of 
this  liquid. 

cxxxvi.  That  fire  is  contained  in  the  blood  is 
proved  from  its  heat,  which,  in  man  and  fimilar 
animals,  is  from  93  to  100  degrees,  which  is  higher 
than  the  mean  degree  of  atmofpherical  heat,  but 
lefs  than  the  greateft.  Befides,  from  blood,  when 
di’awn,  fomething  volatile  or  halituous,  with  a pecu- 
liar odour,  intermediate  between  that  of  the  fweat 
and  urme,  efcapes.  When  collected  in  proper  vef- 
fels,  it  appears  aqueous,  v.ith  a flight  tincture  of  an 
alkaline  nature. 


cxxxvii. 


BLOOD. 


Chap.  V. 


6i 


cxxxvii.  After  the  cfcape  of  this  vapour,  the 
blood  of  a healthy  perfon,  fpontaneoufly  congeals 
into  a tremulous  fcifiile  mafs ; but  with  a degree 
of  heat  lefs  than  that  of  boiling  water,  (and  indeed 
at  150°)  it  coagulates  more  completely  even  when 
perfedly  healthy,  though  more  efpedally  when  tak- 
en from  a febrile  perfon.  It  fometimes  coagulates 
in  the  veins  of  a living  perfon,  and  is  found  clot- 
ted in  wounds  of  arteries.  Even  in  a living  per- 
fon, and  in  one  dying  from  the  violence  of  fever, 
the  blood  has  been  coagulated  into  a tremulous 
jelly  throughout  all  the  veins.  The  principal  part 
of  this  coagulum  is  the  cruor,  which  has  the  red 
colour  peculiar  to  itfelf,  and  imparts  it  to  the 
other  parts  of  the  blood.  This,  condenlible  by- 
reft,  or  a moderate  degree  of  cold,  and  coagulable 
into  a liver-like  mafs  by  a heat  of  150°,  alcohol* 
or  the  mineral  acids,  is,  ho-vvever,  foft,  unlefs  hard- 
ened by  the  attrition  of  life,  or  equivalent  agita- 
tion. It  is  ponderous,  and  heavier  than  water  by 
nearly  an  eleventh  part  ; and,  when  freed  from 
its  water,  it  is  wholly  inflammable.  In  the  mafs 
of  blood,  one  half  or  upwards  is  cruor  ; and,  in. 
ftrong  I'obuft  people,  the  ferum  makes  only  a third 
part  ; in  fevers,  it  is  diminiflied  to  a fourth  or 
fifth  part  j and  in  difeafes  from  debility,  it  is  in- 
creafed. 

cxxxviii.  From  this  coagulum  there  feparates* 
as  it  were  fweating  out  of  its  pores,  but  afterwards 
colledling  in  fufhcient  quantity  to  allow  the  coagu- 
lum  to  fink  in  it,  another  part  of  the  blood  which 
is  white  or  fomewhat  yellowiih,  and  alfo  feemingly 
homogeneous,  though  it  is  not  fo.  This  part  o£ 
the  blood  is,  in  general,  one  thirty-eighth  part  heav- 
ier than  water,  and  almoft  a twelfth  part  lighter  than 
the  red  globular  mafs  ; coagulable  by  a heat  of  150® 
or  the  addition  of  mineral  acids  or  alcohol,  or  by 
agitation  ; it  produces  a firm.er  coagulum  than  the 
red  cruor  (cxxxvn.)  and  concretes  into  an  in- 

foluble 


62 


BLOOD. 


Chap.  V. 


foluble  gluten,  acquires  a membranous  appearance, 
and  finally  a horny  hardnefs,  with  a friability  like 
that  of  gum.  Of  it  are  formed  the  pleuritic  crufts, 
polypufes,  and  artificial  membranes.  In  the  ferum, 
befides  this  coagulable  albumen,  there  is  contained 
fimple  water,  which  conlUtutes  the  principal  part 
of  the  whole  ; and  fome  mucous  matter,  capable 
of  being  drawn  into  finer  threads  than  the  red  cru- 
or  ; and  not  coagulable  by  fire  or  by  acids  as  the 
albumen. 

cxxxix.  Putrefaction  alone,  and  the  influence 
of  a temperature  of  96"  diffolves  into  a fetid  liquor 
the  whole  blood,  but  efpecially  the  ferum  ; fir  ft 
the  ferum,  and  then  the  cruor  more  flowly  ; till, 
at  length,  tire  whole,  both  cruor  and  lymph,  is 
changed  into  a volatile  and  feted  exhalation  ; leav- 
ing very  few  feces  behind.  The  blood,  when  fome- 
what  diffolved  by  putrefaction,  both  before  it  be- 
comes fetid,  and  while  fetid,  evinces  an  alkaline 
nature,  and  efi'ervefees  with  acids.  Thence,  in 
confequence  of  putrefaction,  it  furiliflies  lefs  alka- 
line fait.  When  putrid,  it  cannot  by  any  art  be 
infpift’ated  ; it  is  alfo  very  difficult  to  refolve  it  af- 
ter it  has  been  coagulated  by  fpirit  of  wne.  By 
too  fevere  exercife,  heat  of  the  atmofphere,  and  ma- 
lignant diforders,  the  cohefion  of  the  blood  is  dif- 
folved, and  it  aiTumes  an  alkaline  nature  almoft  as 
if  from  putrefaction. 

GXL.  Befides  thefe  conftituents  of  the  blood, 
which  are  demonftrated  without  fabjecTing  it  to 
any  violence,  it  alfo  contains  a quantity  of  fea-falt, 
wliich  is  difcernible  by  llie  tafte,  and  fornctimes  by 
the  microfeope.  Both  nutrition  and  chemical  an- 
alyfis  deinonftrate,  that  the  blood  alfo  contains 
earth,  which  is  contained  in  the  meft  nuid  parts, 
and  efpecially  united  with  the  oil.  By  fome  very 
late  experiments,  it  appears,  that  a conliderable 
quantity  of  ferrugineous  calx,  eallly  reducible  into 
a true  metal  by  the  addition  of  any  infiainmalde 

body. 


Chap.  V. 


BLOOD. 


63 

body,  is  contained  in  calcined  cruor.  Laftly,  there 
is  mixed  with  the  blood  condenfed  air,  and  that 
in  a very  confiderable  quantity  ; the  exigence  of 
which  in  the  blood  and  ferum  is  proved  by  putre- 
faction, or  by  removing  the  prelTure  of  the  ambi- 
ent air.  The  blood  globules  are  not,  on  this  ac- 
count, air  bubbles,  for  they  are  fpecihcaily  heavier 
than  the  ferum. 

cxLi.  By  the  admixture  of  neutral  fklts,tlie  col- 
our of  the  blood  becomes  deeper  and  brighter,  as 
by  them  it  is  neither  diffolved  nor  thickened.  It 
is  fcarcely  altered  by  weak  acids.  By  ftrong  ones 
it  is  coagulated.  Tixed  alkaline  falts  have  aknoft 
the  fame  effects  as  the  neutrals.  The  volatile  alka- 
lies rather  turn  it  larown,  and  coagulate  it.  Alco- 
hol and  diltilied  oils  coagulate  it  like  krong  acids. 
It  does  not  eflervefce  with  any  fait. 

cxLii.  Chemiftry  has  opened  various  ways  for 
iriveftio:atLn<y  the  nature  of  the  blood.  From  blood 
recently  drawn  and  perfeftly  frelh,  by  expofure 
to  a gentle  degree  of  heat,  there  is  diltilied  a large 
quantity  of  water,  compoling  five-fixths  of  the 
whole  or  more,  almoft  inlipid,  though  impregnat- 
ed with  feme  fetid  oil,  more  krongly  as  the  dif- 
tillation  proceeds. 

The  reliduum,  expofed  to  a kronger  kre,  yields 
various  alkaline  liquors  ; of  which  the  firk,  acrid, 
fetid,  and  of  a reddiki  colour,  is  ufualiy  called  the 
ipirit  of  blood  ; it  conliks  of  volatile  fait  and  oil, 
dilfolved  in  water,  and  amounts  to  one-twentieth 
part  of  the  original  mafs  of  blood.  There  is,  more- 
over, an  acid  in  fat,  and  in  kelh  even  when  putrid, 
and  in  blood. 

Both  before,  and  along  with  the  oil,  that  next 
afcends  in  the  dikillation,  a dry  volatile  fait  arifes, 
and  adheres  in  branchy  keeces  to  the  neck  of  the 
retort ; its  quantity  is  fmali,  about  an  eightieth  part. 

Another  kuid,  gradually  thicker  and  heavier,  at 
firk  yellow,  then  black,  and  iakly  of  a pitch)'-  te- 
nacity. 


BLOOD. 


Chap.  V.. 


64 

nacity,  acrid  and  inflammable,  is  the  oil  of  human 
blood.  - Its  quantity  is  fmall,  about  the  fiftieth  part. 
There  now  remains,  in  the  bottom  of  the  retort, 
the  fpongy  and  inflaminable  cinder  of  the  blood, 
which,  being  kindled,  deflagrates,  and  leaves  aflies 
behind.  From  thefe,  by  lixiviaiion,  is  obtained  a 
fait,  confifting  of  fea-falt,  mixed  with  fixed  alkali, 
and  a fmall  quantity  of  infipid  earth.  This  fixed 
fait  is  fcarcely  the  five  hundredth  part  of  the  firft 
mafs,  and  of  this  almoft  one-fourth  is  alkaline  : 
when  fubjedted  to  an  intenfe  degree  of  fire,  it  af- 
fords a little  acid,  which  we  fappofe  to  arife  partly 
from  the  fea-falt,  fimilar  to  that  demonftrable  in 
the  fpirit  of  blood;  and  partly  from  the  vegetable 
nature  of  our  aliments,  not  yet  completely  ar.ima- 
iyzed.  Hence  it  is  found  in  herbivorous  animals, 
as  well  as  in  man.  But  the  earth,  which  is  about 
the  hundred  and  fiftieth  part,  contains  feme  parti- 
cles which  are  attracted  by  the  loadflone. 

cxLiii.  This  analyfis  fliews  that  the  blood  con- 
tains various  fluids,  feme  more  heavy  and  tenacious 
than  others,  feme  aqueous,  others  inflammable,  and 
that  moft  of  them  impart  to  the  blood  a putrid  or 
alkalefcent  tendency.  For,  the  blood,  when  heal- 
thy, and  not  injured  by  putrefacHon,  or  too  vio- 
lent a degree  of  heat,  is  neither  alkaline  nor  acid  ; 
but  bland,  and  fomewhat  fait,  although,  in  fome 
difeafes,  it  is  very  acrid  and  almoft  putrid  ; as,  for 
inftance,  in  feurvey,  where  it  corrodes  its  contain- 
ing vefiels ; and  in  dropfies,  the  waters  of  which 
are  nearly  alkaline.  In  infecls,  there  is  found  an 
alkalefcent  calx  which  eftervefees  with  acids. 

cxLiv.  By  viewing  with  the  microicope  frefli 
blood  in  a fmall  glafs  tube,  or  while  it  is  yet 
movinu  in  the  veins  of  a warm  blooded  livincf  ani- 

O O 

mal,  as  a cliicken,  or  of  a cold  one,  as  a frog,  we 
perceive  in  it  red  globules  ; which  doubtlcfs,  con- 
ftitute  the  cruor  mentioned  in  cxxxvii.  Or  are 

they 


BLOOD. 


Chap.  V. 


they  rather  lenticular  particles  of  the  fame  kind 
withlhofe  obferved  by  Leeuwenhoeck  in  filhes,  and 
lately  difcovered  in  our  own  fpecies  ; it  is  difficult 
to  determine  i nor,  often  as  I have  ufed  the  mi- 
crofcope^  have  I ever  miffed  thofe  fliadows  in  the 
globules  which  indicate  thicknd^s  and  convexity. 

cxLv;  The  colour  of  thefe  globules  is  red;  and 
fo  much  the  deeper,  and  more  inclined  to  fcarlet, 
the  llronger  the  animal  is  ; and  in  the  fame  propor- 
tion, their  number  increafes,  when  compared  with 
the  yellow  ferum.  Their  diameter  is  fmall,  being 
between  ^boo  and  Tsbo  of  an  inch.  They  are  faid 
to  change  their  figure  into  an  oblong  egg  like 
lliape,  v/hich  I have  never  been  able  to  obferve 
with  fufficient  certainty.  They  are  ajfo  faid  to 
break  down  into  other  leffer  globules  of  a yellow 
colour,  which  I have  neither  obferved  myfelf,  nor 
can  eafily  admit. 

cxLVJ.  Fibres  are  obtained  in  great  quantity 
from  the  blood,  and  more  fparingly  from  the  fe- 
rum, by  gradually  waffling  it,  when  poured  on  a 
linen  cloth,  with  much  water  ; or  by  beating  with 
rods,  blood  poured  into  water  : they  will  amount 
to  one  eighty-fifth  part  of  the  whole.  Thefe  are 
formed  of  the  gluten,  and  do  not  exift  in  the  liv- 
ing animal ; fince  they  neither  are  perceived  by  the 
microfcope,  which  yet  fo  eafily  renders  vifible  the 
red  globules,  although  fo  much  fmaller,  nor  is  theii* 
long  thread  like  figure  adapted  for  receiving  mo- 
tion. 

cxLvii.  From  the  preceding  experiments  com- 
pared together,  arifes  that  knowledge,  which  wc 
at  prefent  have  of  the  blood;  namely,  that  the 
cruor  is  compofed  of  globules.  The  inflammable 
nature  of  thefe  globules  is  proved  by  the  inflam- 
mation of  dried  cruor,  and  the  preparation  of  py- 
rophorus  from  human  blood ; and,  from  thele, 
moil  probably,  proceeds  the  greater  part  of  the 
F pitchy 


66 


BLOOD. 


Chap.  V. 


pitchy  oil  that  is  obtained  frOm  blood  by  the  acUon 
of  lire. 

cxLviii.  The  ferum  of  the  blood,  fubjecled  to 
the  aclion  of  fire,  yields  almoft  the  fame  principles 
with  the  red  blood,  viz.  fait,  oil,  and  earth,  but 
more  water  and  n6  iron.  Similar  principles,  but 
with  a lefs  proportion  of  oil  and  fait,  are  obtained 
from  tlie  aqueous  humours  formed  from  the  blood ; 
as  the  faliva,  and  mucus. 

cxLix.  The  quantity  of  blood,  contained  in  the 
wliole  body,  cannot  be  very  certainly  computed. 
I he  weight  of  the  fluids,  however,  is  much  greater 
than  that  of  the  lolids ; but  many  of  them,  as  the 
gluten  in  various  parts,  and  the  fat,  do  not  circu- 
late. But  if  we  may  be  allowed  to  form  a judgment, 
from  thofe  profufe  hemorrhages  that  have  been  fuf- 
tained  without  deflroying  the  life  of  the  patient ; 
from  experiments  made  on  living  animals  by  ex- 
iracfino;  all  their  blood  ; and  from  the  canacitv  of 
the  arteries  and  veins ; there  will  be  at  leaf!  fifty 
pounds  of  fluids  vdiich  circulate,  of  which  about 
twenty-eight  will  be  true  blood  : the  arteries  con- 
tain about  one-fifth,  and  the  veins  the  other  four 
parts. 

CL.  Nor  are  the  proportions  of  the  elements, 
which  we  have  hitherto  m.entioned,  conftant ; for, 
an  active  life,  manhood,  and  fever,  increafe  the 
cruor,  rednefs,  coagulability,  cohefion  of  the  parts, 
firmncfs  of  the  coagulated  ferum,  weight  and  alka- 
line principles.  The  ferum,  and  the  mucus  if  con- 
tains, are  increafed  by  the  contrary  caufes  ; a lefs 
mature  age,  inactive  life,  and  a watery  and  vegeta- 
ble diet ; by  all  which,  the  crahamentum  of  the 
blood  is  lefiened,  and  its  watery  part  increafed. 
Old  ac-e,  affain,  auerments  the  cruor,  and  diminiflies 
the  gelatinous  part. 

CLi.  On  tLefe  principles,  conjoined  vdth  a con- 
fideration  of  the  folid  ftruclure,  the  divcrlity  of 
temperaments  depends.  For  plethora  arifes  from 


Chap.  V. 


BLOOD. 


67 

an  abundance  of  the  red  globules  ; a phlegmatic 
temperature,  from  a redundancy  of  the  watery  part 
of  the  blood ; a choleric  difpofition  in  the  fluids 
feems  to  proceed  from  a more  acrid  and  alkalefcent 
nature  of  the  blood ; as  in  thofe  who  live  on  flefh^ 
and  in  anthropophagi,  who  appear  to  be  more  fierce 
than  thofe  who  live  on  vegetable  food.  In  the  fol- 
ids,  greater  irritability,  and  hardnefs,  with  mobili- 
ty, are  attributed  to  a choleric  habit  ; a lefs  irrita- 
bility, with  a more  moderate  denfity,  to  a fanguine 
habit  ; and  lefs  denfity,  and  lefs  irritabilty,  to  a 
phlegmatic  temperament.  There  is  alfo  a fluggifh 
temperament,  in  which  remarkable  ftrength  of  body 
is  joined  with  little  irritability.  In  the  melancho- 
lic, exceffive  irritability  feems  united  with  debility. 
But  we  mufl;  be  cautious  not  to  clafs  too  fyftemat- 
ically  the  temperaments,  which  in  nature  are  not 
four  or  eight,  but  infinite  in  their  varieties. 

CLii.  The  generation  of  heat  feems  to  be  the 
principal  ufe  of  the  red  cruor,  as  its  quantity  is  in 
proportion  to  the  temperature  of  the  blood.  Being 
confined,  by  the  largenefs  of  the  globules,  within 
the  firfl:  order  of  veflels,  it  hinders  them  from  col- 
lapfing ; and,  in  receiving  the  common  impulfe  from 
the  heart,  on  account  of  the  greater  denfity  of  its 
parts,  it  acquires  a greater  impetus,  and  fets  in 
motion  the  inferior  orders  of  hum.ours.  Nor  is  it 
improbable,  that  the  heart  is  more  duly  excited  by 
the  ponderous  cruor.  The  globular  figure  of  its 
parts,  imparts  to  it  fluidity  conneded  with  denfity ; 
that  quality,  and  perhaps  the  power  of  generating 
heat,  are  increafed  by  the  quantity  of  iron  and  of 
oil.  Hence,  when  the  red  part  of  the  blood.is  too 
much  diminifhed  by  bleedings,  there  follows  a 
flagnation  in  the  fmaller  veflels  ; fatnefs  and  dropfy. 
From  the  fame  reafoning,  a due  proportion  Of  cru- 
or feems  neceflary  for  the  generation  of  new  blood. 
For,  in  confequence  of  hemorrhages,  the  blood  de- 
generates 


blood: 


^8^ 


Chap.  V, 


generates  from  its  red  and  denfe  nature,  into  a pale 
and  ferous  ftate. 

CLiii.  The  coa-gulable  ferum  is  more  efpecially 
deligned  for  the  nutrition  of  the  parts,  as  will  be 
hereafter  fliewn,  chap.  xxx.  The  thinner  fluids 
ferve  various  purpofes  ; as,  the  diflblution  of  the 
aliments,  the  moiflening  the  external  furface,  and 
furfaces  of  the  internal  cavities  of  the  human  body, 
to  preferve  the  flexibility  of  the  folids,  and  conduce 
to  the  motion  of  the  nerves,  the  fight,  &c.  The 
faline  particles  feem  proper  for  diflblving  the -ali- 
ment, and  llimulating  the  veffels.  The  properties 
of  the  aerial  part  are  not  yet  fufficiently  known. 
The  heat  produces  its  fluidity,  and  is  not  eafily 
raifed  to  fuch  a degi'ee  as  to  coagulate  the  fluids  of 
the  human  body. 

cniv.  Therefore,  health  can  neither  fubfifi;  with- 
out the  thick  blood,  and  a diminution  of  its  quan- 
tity caufes  a ftagnation  in  all  the  fmaller  veiTels, 
and  univerfal  palenefs,  coldnefs  and  debilty  : nor 
can  the  functions  of  human  life  or  health  fublifl: 
without  the  fluids  of  the  inferior  orders,  fince  the 
cruor,  deprived  of  its  watery  part,  congeals  and 
obftructs  the  paflages  of  the  veffels,  and  produces 
too  great  a heat. 

CLv.  Is  there  any  difference  betwixt  the  arte- 
rial and  venous  blood  ? It  feems  probable,  as  the 
former  has  lately  fuffered  the  action  of  the  lungs. 
But,  in  experiments,  I fcarcely  find  any  difference 
obfcrvable,  either  in  colour,  denfity,  or  any  other 
property  5 although,  in  other  fituations,  I have  feen 
it  very  apparently,  for  the  bright  red  colour  of  the 
art  crial  blood  feems  to  diffinguHh  it  from  the  dulky 
dark  coloured  blood  in  the  veins  ; but  this,  in  the 
plain  example  of  the  chick  in  ovo,  arifes  only  from 
the  feries  of  stlobules  beinsr  deeoer  in  the  thicker 
vein.  Nor  is  there  any  eftabliflied  difference  in  the 
blood  of  different  arteries. 


CLVIr 


Chap.  VI. 


ARTERIES. 


J&9 

cLvi.  From  the  fame  blood,  driven  Into,  the 
aorta,  are  generated  all  the  fluids  of  the  human 
body.  Thefe  are  red.ucible  to  certain  claffes.  The 
means  by  which  they  are  feparated,  ought  to  be 
accounted  for  by  the  fabric  of  the  glands.  But 
muft  firft  confider  what  the  blood  fuffers  from  its 
containing  veflels. 

CHAP.  VT. 

OF  THE  COMMON  FUNCTIONS  OF  ARTERIES. 

CLVii.  ^ g '•HE  blood,  driven  from  the  left  ventri- 
1 cle  of  the  heart  into  the  aorta,  which, 
at  its  origin  from  the  heart,  bends  firfl;  a little  to- 
wards the  right,  and  then  to  the  left,  and  back- 
wards, in  a very  acute  arch,  ftrikes,  in  a mafs,  firft 
againft  the  right  fide  of  the  aorta,  and  is  then  re- 
flecled  to  the  left-  fide ; whence,  with  a rotatory 
motion,  as  much  as  their  fulnefs  permits,  it  pro- 
ceeds through  the  arteries,  alternately  ftri-king  and 
rebounding  from  their  fides.  The  fize  of  the  aorta 
is  a little  increafed,  where  it  arifes  from  the  heart, 
CLviii.  The  arteries  are,  in  a living  perfon,  always 
full  of  blood  5 fince  the  blood  fpringing  from  an 
artery,  is  not  interrupted  by  alternate  flops  during 
the  relaxation  of  the  heart,  but  flows  on  in  a con- 
tinued ftream,  and  the  microfcope  fliews  the  arte- 
ries, in  living  animals,  to  be  full,  both  in  their  fyf- 
tole  and  diaftole ; nor  can  the  circular  fibres  of  the 
arteries  contracl  themfelves  completely,  or  entirely 
evacuate  thefe  tubes.  Therefore,  when  into  the 
full  arteries  there  comes  a new  wave  of  blood,  al- 
though it  fcarcely  exceeds  two  ounces,  and  bears 
a fmall  proportion  to  the  arterial  fyftem  tlirougli- 
out  the  body ; it,  however,  overtakes  the  preceding 
wave,  which  being  farther  from  the  heart,  moves 
flower  j it  confequently  drives  tlic  iame  forwards, 

IpncrflirnfSi 


O 


ARTERIES. 


CiiAP.  YL 


70 

lengthens  the  cylindrical  artery,  augments  its  di- 
ameter, preffes  the  membranes  clofer  to  one  another, 
urges  the  convex  parts  of  its  flexures  outwards,  and 
produces  more  ferpentine  turns,  as  injections  de- 
monftrate.  This  dilatation  of  the  artery,  and  change 
of  its  caliber,  from  a lefs  to  a greater  circle,  is  call- 
ed the  pulfe  ; the  diaftole  of  which,  is  an  expan- 
flon  of  the  artery  beyond  its  natural  diameter.  It 
is  peculiar  to  life,  and  refults  from  the  heart  only, 
and  is  not  naturA  to  arteries  left  to  themfelves. 
Hence,  yrhen  the  motion  of  the  heart  is  intercep- 
ted, whether  its  im.pulfe  be  obftimcled  by  aneurifin, 
or  ligature,  there  is  no  pulfation  ; and  hence,  the 
flidden  ceflation  of  the  pulfe,  in  a living  animal, 
on  the  heart  being  perforated.  The  artery  is 
proportionally  more  dilated,  the  more  flowly  the 
preceding  wave  of  blood  efcapes,  and  the  more 
the  velocitv  of  the  new  wave  exceeds  that  of  the 
former. 

CL IX.  The  contraction  of  the  artery  fucceeds  its 
dilatation.  For  the  heart,  having  emptied  itfelf, 
and  removed  the  fcimulus  of  the  blood,  becomes 
quiefeent.  Eut  the  artery,  at  that  inftant,  by  the 
innate  elafticity  refiding  in  its  circular  fibres, 
being  irritated  by  the  fame  ftimulus  of  blood 
thrown  into  it,  contracts  ilfelf,  and  expels  as  much 
of  the  blood  as  it  had  received  above  its  mean  ca- 
pacity ; the  whole  of  this  quantity  pafles  either  into 
the  fmallcr  vcflcls,  or  into  the  veins  ; for  the  femi- 
lunar  vah  es  of  the  aorta  prevent  its  reflux  into  the 
heart.  So  foon  as  the  arteiy  has  freed  itfelf  from 
this  wave,  being  no  longer  ftiinulated,  it  remits  its 
contracl'ile  aftion,  and  immediately  yields  to  a new 
wave,  propelled  by  the  heart ; and  a new  diaftole 
enfues. 

CLX.  That  the  arteries  contract,  and  by  that 
means  propel  the  blood,  is  proved  by  their  contrac- 
tile nature  ; by  the  evident  remifnon  of  the  dilata- 
tion caufed  by  the  heart ; by  the  fpontaneous  eva- 
cuation 


Chap.  VI.  ARTERIES.  71 

cuation  of  an  artery  through  its  lateral  hranches, 
included  between  two  ligatures  ; by  the  return  of 
the  blood  to  the  heart,  after  its  artery  is  tied,  which 
blood,  therefore,  is  not  propelled  by  the  heart ; by 
the  jet  of  blood  from  arteries  being  greater  during 
the  relaxation  of  the  heart,  as  obferved  by  emi- 
nent anatomifts;  by  the  vigorous  projection  of  blood 
from  the  aorta  when  tied,  below  the  ligature  ; by 
the  evacuation  of  the  arteries  during  the  perfeft 
quiefcence  of  the  heart  ; by  the  veins  being  fuller 
than  the  arteries  after  death  ; by  the  coniiderabie 
jet  of  blood,  to  the  extent  of  two  feet,  from  the 
aorta  in  an  animal  after  death  ; by  the  fmail  cali- 
ber of  the  ill  filled  arteries  in  a famiflied  animal  ; 
by  the  clofing  of  their  orifices  in  wounds  ; and  by 
the  fphacelation  of  limbs,  whofe  arteries  are  ofiifi- 
ed,  and  the  veins  being  in  that  cafe  diftended  with 
blood. 

CLxi.  The  mean  velocity  of  the  blood  may  be 
computed,  by  diminifliing  its  velocity  during  the 
fyftole,  as  much  as  we  increafe  what  remains  of  it 
during  the  diaftole,  to  be  nearly  fuch,  as  to  move  at 
the  rate  of  two  feet  in  a fecond.  The  conftaiit 
plenitude  of  the  arteries,  is  the  reafon  why  we  can- 
not perceive  any  fucceflion  in  the  pulfations  of  dif- 
ferent arteries,  and  that  in  the  Iiuman  body  they 
all  feem  to  beat  at  one  inftant,  and  at  the  fame  time 
that  the  heart  ftrikes  againft  the  breaft.  However, 
there  certainly  is  a fucceflion,  and  the  contractions 
of  the  aorta  appear  to  follow  in  the  fame  order,  as 
its  repletion  with  the  blood,  expelled  by  the  heart, 
fo  that  the  part  of  the  artery  next  to  the  heart  con- 
trafls  firft,  and  that  thus  the  contraHions  proceed 
gradually  to  the  ultimate  arteries.  This  is  appar- 
ent in  the  example  of  the  inteftines,  and  may  be 
feen  in  infecfs,  whofe  long  and  knotty  heart  mani- 
feftly  contraHs  fucceflively  from  the  beginning  to 
the  end.  But  the  mind  of  the  obferver  cannot  dif- 


ARTERIES. 


Chap..  VI. 


tingullh  the  minute  portion  of  time,  which  amountsi 
only  to  a few  thirds. 

CLxii.  Where  does  thepulfe  ceafe  ? In  my  opin- 
ion, in  the  uitima.te  and  cylindrical  arteries.  We 
have  noticed  v/ith  what  velocity  the  blood  iffues 
from  the  heart.  But  that  velocity  continually  de- 
cre?.fes.  It  is  certain,  that  the  aggregate  capacity 
, of  the  fmali  arteries,  always  bears  a larger  propor- 
tion to  the  capacity  of  the  aorta,  as  their  divihcn 
proceeds  farther  ; and  thus,  notwithftanding  the  dif- 
ference in  the  proportion  between  the  trunks  and 
their  branches  a'vaays  decreases,  this  proportion 
will  be  greatell,  although  it  may  be  variable,  be- 
tween the  aggregate  capacity  of  the  fmall  arteries 
in  their  ultimate  divilion,  and  the  capacity  of  the 
aojta  at  its  origin  ; and  there  wall  be  a fimilar  re- 
tardation of  blood  to  that  which  occurs  in  aneu- 
rifms.  Beiides,  the  proportion  of  the  coats  of  the 
arteries  to  their  calibers  always  increafes  as  they 
are  fmaller,  until  it  is  greateft  v'here  they  tranfmit 
the  glol'/iilcs  fmgly.  This  is  proved  from  di  flec- 
tion ; from  inflation,  by  which  every  thing  bcin^ 
reckoned,  they  arc  always  more  difficultly  ruptured 
as  they  are  fmaller  ; and  by  calculation,  which  efti- 
mates  tlie  fize  of  the  globules  by  the  cylindrical 
membranes  of  the.  ultimate  arteries.  Add  to  tliis, 
the  friction  of  a liquid  pafling  through  minute  and 
long  tubes,  bent  and  uniting  at  angles  ; which  kind 
of  friclion  diminilhcs  remarkably  the  velocity  even 
of  fluid  water  pafling  through  Ample  and  merely 
long  tubes,  and  this  always  in  proportion  to  their 
fmallnefs ; and  befldes,  the  fmaller  an  artery  is,  the 
greater  number  of  globules  come  in  contact  with 
its  tides,  and  rub  againfl:  them.  In  confequence  of 
the  conical  form  of  the  arteries,  the  broader  wave 
of  blood  coming  from  the  trunk  cannot  pafs  with- 
out rcfiftance  through  the  linaller  aperture  of  the 
bran.h,  and  without  endeavouring  to  diftend  the 
branch  ; but  alfo,  t|ie  influctiens  and  folds  retard 

the 


Chap.  VT. 


ARTERIES. 


73 

the  blood  ; fince  feme  part  of  the  impelling  force 
is  always  fpent  in  impinging  on  the  convex  part  of 
the  fold,  and  in  the  change  of  the  figure  of  the  in- 
flected veffel.  Large  angles  likewife  diminifli  the 
velocity,  in  proportion  as  they  are  more  obtufe,  and 
recede  from  a ftraight  line.  Moreover,  the  vifeid- 
ity  of  the  blood  itl'elf  muft  be  taken  into  confider- 
ation  ; fince,  by  reft  alone,  it  immediately  con- 
cretes into  clots  ; and  fince  it  is  from  the  circula- 
tory motion  only  that  this  mutual  attraction  of  co- 
hefion  in  its  parts  is  overcome,  fo  as  to  prevent  it 
from  adhering  to  the  fides  of  the  arteries,  as  it  ad- 
heres in  aneuriims  and  wounds  ; and  the  globules 
from  concreting  together,  as  they  ufually  do  after 
death.  The  oppofition  it  meets  with  in  the  branch- 
es, leffens  the  velocity  of  the  blood  likewdfe  in 
the  trunk  : the  oppofite  currents  of  blood  in  anai- 
tomofes  alfo  deftroy  fome  part  of  its  motion.  Hence 
the  immenfe  retardation  of  the  blood  in  the  minute 
veflels.  . We  may  eafily  perceive  that  it  is  very 
confiderable,  although  it  is  difiicult  to  eftimate  it. 
In  the  living  animal,  the  blood  flows  in  the  trunk 
wdth  the  rapidity  of  a torrent ; in  the  minute  ar- 
teries, it  for  the  moft  part  begins  to  move  flowly, 
and  then  to  be  coagulated.  It  is  alfo  well  known 
to  furgeons,  that  a flnall  branch  of  a.n  artery  near 
the  heart  or  aorta,  bleeds  more  dangeroufly  than  a 
much  larger  one  that  lies  at  a greater  diftance.  The 
v/eight  of  the  incumbent  atmofpherc,  of  the  mufcles 
and  flefliy  parts  lying  above  the  arteries,  and  the 
contractile  power  of  the  veflels,  make  a refiftance 
indeed  to  the  heart,  but  do  not  lelfen  the  velocity 
of  the  blood,  for  they  add  as  m.uch  during  the  diaf- 
tole  of  the  heart,  as  they  take  away  from  its  powers 
during  the  tidtole. . 

CLxiii.  It  ip  certain,  hovrever,  from  incifions 
m.ade  in  living  animals,  that  the  globules  of  bloodj 
which  move  fingly,  do  not  iofe  fo  much  of  their  ve- 
locity as,  by  calculation,  they  ought  to  do.  There 

muft. 


ARTERIES. 


Chap.  VI. 


74 

rnufl,  therefore,  exift  feme  caufes,  which  diminlfh 
the  powers  impeding  their  motion.  And,  indeed,  it 
is  certain,  that,  in  the  minute  velfeis,  the  calibers  of 
the  branches  do  not  bear  fo  great  a proportion  to 
the  trunk  j their  great  fmoothnefs  alfo  diminifhes 
the  friction.  The  facility,  likewife,  with  which  the 
blood  returns  through  the  veins,  expedites  its  paf- 
fage  through  the  ultimate  arteries  which  imme- 
<liately  communicate  with  thefe  veins.  No  great 
effed:  can  be  expected  from  the  weight  of  the 
blood,  from  the  action  of  the  nerves,  or  from  their 
plexufes,  of  which  the  firft  may  both  retard  and 
accelei'ate  occalionally,  and  in  living  animals,  the 
two  laft  have  no  effect  whate^'er.  The  power  of 
derivation,  whatever  that  is,  and  mufcular  adion, 
are  capable  of  producing  an  increafe  of  vel'^-  ity. 

CLxiv.  The  pulfe  is  therefore  generated  by  the 
anterior  wave  of  blood  Sovung  more  howly,  while 
the  fabfequent  wave  hows  fafter  ; fo  that  the  form- 
er is  an  obftacle  to  the  latter  (cnviii.)  But  iince 
the  motion  imparted  to  the  blood  by  the  heart 
weakens  in  its  progrefs,  and  the  contradile  power 
of  the  arteries  increafes,  therefore  the  cxcefs  of 
celerity  of  the  pofterior  veave,  which  comes  from 
the  heart,  above  that  moved  by  the  contraefion  of 
tiie  minute  veffels,  \rill  be  continually  Icffening, 
till,  arriving  at  a part  where  tliere  is  no  excels, 
the  pulfe  will  there  ccafc,  from  tlic  anterior  and 
pofterior  waves  both  flowing  with  the  fame  ve- 
locity, and  therefore  in  one  ftream.  I'his  place 
will  not  be  in  the  larger  branches  ; for  in  them, 
the  wave,  laft  coming  from  the  heart,  moves  quick- 
er than  what  goes  before  ; as  is  evident  from  the 
inflammatory  pulfation,  efpecially  of  the  fmali  ar- 
teries of  the  eye.  But,  in  the  ultimate  arteries,  the 
pulfe  vaniflies.  This  is  evident  from  the  equable 
motion  of  the  blood  in  the  minute  arteries,  often 
feen  by  the  microfeope  in  frogs.  Even  in  vef- 
fels  fomewhat  larger,  the  flxth  part  of  a line  in 


Chap.  VI. 


ARTERIES. 


75 


diameter,  the  ptslfe  ceafes  to  be  perceptible  iii’the 
living  arximal.  In  the  veins  vifible  by  the  micro- 
fcope,  there  is  no  puHation  or  acceleration  of  the 
blood,  whilft  the  heart  contracts,  demonftrable  ei- 
ther by  the  microfcope  or  in  any  other  way. 

CLxv.  Even  in  the  veins,  the  blood  preffes 
againit  their  fides,  as  appears  from  the  furrows 
hollowed  out  in  the  bones,  and  the  fwelling  of  the 
veins  on  being  tied.  AVhy  do  not  the  veins  beat  ? 
for  we  do  not  allow  that  to  be  a pulfe  which  is 
caufed  by  refpiration,  or  by  the  regurgitation  of 
blood  from  the  right  auricle,  or  mufcular  part  of 
the,  vena  cava.  The  reafon  feems  to  be,  that  the 
blood,  when  it  immediately  leaves  the  heart,  is 
more  retarded,  and  in  the  ultimate  arteries,  lefc. 
Hence  the  Ihort  fpace  of  time  by  vchich  the  ve- 
locity of  the  laft  wave  exceeds  the  foregoing,  is 
greateft  at  the  heart,  and  groves  gradually  lefs,  till 
•at  laft  it  totally  vanilhes.  The  following  experi- 
ment is  appolite.  Water  forced  in  jets  through  a 
leathern  tube,  by  means  of  a fyringe,  flows  out  of 
a bit  of  fponge  fixed  at  the  end  of  the  tube  in  one 
uniform  and  continued  ftream  ; and  alfo  the  anal- 
ogous experiment,  where  the  fame  happens  when 
water  is  thrown,  in  alternate  jets,  into  the  mefen- 
teric' arteries ; for  even  then  the  water  Sows  cut  of 
the  veins  in  one  continued  fiream. 

CLXvi,  The  pulfe  is  the  meafure  of  the  powers 
exerted  by  the  heart,  becaufe  it  is  the  immediate 
and  full  efFefl  of  thofe  powers.  Hence,  all  things 
confidered  as  alike,  the  pulfe  is  flow  in  the  Rate 
of  perfefl  health,  where  there  is  no  ftimulus,  no 
refiflance  acting  as  a ftimulus,  and  the  heart  pro- 
pels the  blood  freely  and  eafJy,  except  whern 
there  is  fome  obffacle,  by  which  the  blood  is  pre.- 
vented  from  entering  the  aorta.  From  that  caufe, 
the  pulfe  in  afthmatic  people  is  flow  : and  alfo 
from  the  debility  or  infenfibility  of  the  heart,  the 
ufual  ftimulus  is 


incapable  or  ftxcitme:  it 

i o 


to  con-i 
tradion. 


ARTERIES. 


Chap.  \T. 


7S 

traiTion.  A full  pulfe  is  caufed  by  the  fuUnefs  of 
the  artery,  joined  with  a ftrong  force  of  the  heart  ; 
» fmall  pulfe  by  the  emptinefs  of  the  artery,  and 
a fmaUer  wave  of  blood  fent  from  the  heart.  A 
hard  pulfe  denotes  forne  obllacle  or  ftimulus,  or 
increafed  aftion  of  the  heart,  with  a greater  thick- 
nefs  of  blood,  or  a greater  rigidity  or  obftruclion 
of  the  artery.  A quick  pulfe  denotes  feme  ftimu- 
lus,  obllacle,  or  greater  fenlibility  and  irritability 
of  the  heart.  The  pulfe  is  bell  felt  where  the  ar- 
tery lies  expofed  and  fupported  by  bone  ; but  ob- 
Ilruclions  fometimes  render  the  pulfe  perceptible  in 
the  moft  oppofite  fitu^tions. 

cnxvii.  The  pulfe  is  ilower  in  animals  as  they 
are  larger  ; becaufe  the  heart  is  proportionably  lefs 
than  ill  fmaller  animals,  and,  as  well  as  the  other 
parts  of  the  body,  is  lefs  irritable,  and  propels  the 
blood  to  a greater  diftarxe  ; and  becaufe  there  feems 
to  be  a greater  increafe  of  friction,  than  of  power 
in  the  heart.  Hence  fmall  animals  are  more  vora- 
cious ; and  large  ones,  as  the  whale  and  elephant, 
eat  lefs.  The  pulfes  of  a healthy  adult  in  the 
morning,  are  at  leaft  65  in  a minute  ; in  the  even- 
ing they  amount  to  80  ; during  the  night  they  a- 
gain  become  lefs  frequent^  and  gradually  return  to 
the  morning  number.  For  mufcular  motion,  the 
action  of  the  external  and  internal  fenfes,  the 
warmth  of  the  atmofphere,  and  food  and  drink, 
urge  the  venous  blood  to  the  heart,  which  being 
thereby  oftner  fUmulated,  makes  more  frequent 
contractions.  This  is  the  caufe  of  tlie  evening  pa- 
roxyfms  obfervable  in  all  fevers.  Sleep  retards  the 
blood  and  every  other  motion. 

CLxviii.  A frequent  pulfe  is  different  from  a quick 
one  ; and  it  is  poffible  for  the  pulfe  to  be  at  the 
fame  time  quick  and  unfrequent.  But  it  is  diffi- 
cult to  pbferve  a quick  pulfe.  The  frequent  pulfe 
is  what  is  commonly  called  a quick  one.  It  13  fre- 
quent  in  ghiidren,*and  becomes  lefs  frequent  in  the 

progrei's 


Chap.  VI. 


ARTERIES. 


77 


progrefs  of  life.  In  the  falient  point,  the  puLfes  are 
134  ; in  new  born  infants,  120  ; and  in  old  people, 
they  decreafe  to  60.  The  febrile  pxilfe  begins  from 
96.  In  fevers,  or  in  an  adult  after  mufcular  action, 
no  or  120  is  a moderate  frequency  : but  it  is  ex- 
ceffive  at  130  or  140,  with  which  number  people 
feldom  recover  ; nor  have  I ever  obferved  it  ex- 
ceed that  number.  The  pulfe  beats  flower  in  win- 
ter, and  quicker  in  fummer,  often  by  10  flrokes  ; 
and  under  (he  torrid  zone,  it  increafes  to  1 20.  The 
pafiions  of  the  mind  difturb  the  pulfe  in  various 
ways.  ■ Whatever  obftructs  the  circulation,  accele- 
rates the  pulfe  5 not  from  the  laws  of  hydroftatics, 
or  on  account  of  the  canal  being  made  narro^ver, 
or  from  the  aflion  of  the  foul ; but  Amply  becaufe 
the  heart  being  with  more  difficulty  freed  from  the 
ftimulating  blood,  contradfs  itfelf  more  ftrongiy, 
and  at  fliorter  intervals.  Irritation  from  acrid 
blood  is  frequently  the  caufe  of  the  febrile  pulfe. 

CL XIX.  Through  the  minute  veins  the  blood 
moves  flowly,  partly  by  the  force  of  the  heart,  and 
partly  by  the  contradtiiity  of  the  arteries.  The  Arfl: 
is  proved  by  a renewal  of  the  motion  of  the  blood, 
in  perfons  drowned,  which  is  effected  folely  by  the 
excitation  of  the  heart.  But  the  contradlile  force 
of  the  arteries  is  proved  by  what  we  faid  in  clx. 

. After  death,  the  blood  is  moved  by  its  own  gravity, 
and  by  the  elaftic  air,  generated  during  its  putre- 
fadtion. 

CLXX.  The  blood  moves  faffer  in  the  larger 
veins.  For  wherever  the  impelling  powers  fuffice, 
and  the  conveying  tubes  are  rendered  narrower,  the 
motion  muff  be  accelerated  ; for  venous  trunks  arc 
fmaller  than  the  branches  of  wffiich  they  are  form- 
ed, in  the  fame  m.anner  as  arteries  are  lefs  than  the 
branches  into  which  they  divide.  Therefore,  if 
the  motion  of  the  venous  blood  loft  nothing  in  its 
W'ay,  the  proportion  of  its  celerity  in  the  vena  cava, 
to  its  celerity  in  the  veins  of  the  thirtieth  diviflon, 

would 


ARTERIES. 


78 


Chap.  VI. 


would  be  exacHy  the  thirtieth  power  of  the  pro- 
portion of  the  funi  of  the  calibers  of  all  the  ulti- 
mate veins,  to  the  caliber  of  the  vena  cava.  At  the 
fame  time  the  friction  is  diminished,  and  the  ccn- 
taft  of  the  blood  with  their  hides. 

CL XXI.  But  since  the  blood  moves  very  flowly  in 
the  ultimate  arteries  and  incipient  veins,  and  as  tlie 
weight  of  the  blood  itfelf,  in  many  places,  impedes 
its  return  remarkably,  and  as,  from  the  very  thin 
coats  of  the  veins,  but  little  contractile  power  can 
be  expected,  nature  has  ufed  various  precautions, 
left,  from  the  flownefs  of  its  motion,  the  venous 
blood  fhould  ftamate  or  concrete.  Therefore  Ihe 

O ^ • • 

has  reft  or  ed  to  the  veins,  the  halitus  and  fluid 
lymph,  in  larger  quantity,  as  it  feems,  than  v'hat 
the  arteries  loft,  on  account  of  the  great  exhalation 
from  the  lungs. 

CLXxii.  She  has  likewife  placed  the  veins  near 
the  mufcles,  which,  by  their  fwelling,  comprefs  the 
interpofed  veins ; and  fince  ea^^ery  preiTure  of  the 
veins,  on  account  of  their  valves,  determines  the 
blood  towards  the  heart  (lxih.)  therefore  all  this 
force  is  entirely  employed  in  accelerating  the  re- 
turn of  the  blood  to  the  heart.  Hence  that  won- 
derful quicknefs  of  the  pulfe  (cLxvii.)  heat,  red- 
nefs,  and  quick  refpiraticn  after  mufcular  action. 

CLXXiii.  Moreover,  thofe  mufcles,  which  ftrong- 
iy  comprefs  on  every  fide  all  the  parts  contained  in 
any  of  the  common  cavities,  powerfully  promote 
the  motion  of  the  venous  blood.  In  the  abdomen,, 
this  is  effected  by  the  conjunft  preffure  of  the  dia- 
phragm and  abdominal  mufcles.  Laftly,  the  pu Ra- 
tions of  the  arteries,  every  where  contiguous  and 
parallel  with  the  veins,  promote  the  return  of  the 
venous  blood  ; ftnce,  as  we  have  before  ihewn,  every 
impulfe  acting  on  the  veins  can  determine  their 
blood  to  the  heart  ordy. 

ci.xxiv.  To  thei’e  is  added  the  p'ower,  not  yet 
fufiiciently  Iviiown,  of  derivation,  by  which  the 

blcoil 


Chap.  VI. 


ARTERIES. 


79 

blood  is  brought  from  a place  where  it  is  more 
compreffed,  to  one  more  lax,  and  where  it  meets 
with  lefs  refiftance.  Laitly,  refpiration  is  of  great 
efficacy  •,  in  which  the  blood  is  ^dternateiy  brought 
by  the  power  of  derivation  from  all  parts  of  the 
body  into  the  fpongy  lungs  ; and  again,  in  exfpi- 
ration,  is  driven  into  the  trunks  of  the  veins  in  the 
head  and  abdomen.  Hence  the  fwelling  of  tlie 
veins,  even  of  the  brain,  in  the  tim.e  of  exlpiration. 
The  circulation  is  not  indeed  affifted  by  thefe  cauf- 
es,  but  the  blood  is  agitated  and  prelTed  forvvards. 
The  anallomofes  have  the  fame  effiecls  as  in  the  ar- 
teries ; for  they  facilitate  the  paffage  of  the  blood 
from  places  where  it  is  obftrudted,  to  thofe  which 
are  pervious. 

- cLxxv.  By  thefe  means,  the  blood  in  a healthy 
perron,  ufing  fufficient  exercife  of  body,  moves  with 
a velocity,  which  is  fufficient  to  reftore,  in  each  pul- 
fation,  to  the  heart,  by  the  vena  cava,  as  much  blood 
as  the  aorta  carried  away.  But  corporeal  inaftioii 
and  debility  of  the  contracting  fibres  of  the  heart 
and  m.ufcles,  frequently  render  the  m.otion  of  the 
venous  blood  more  difficult.  Hence  the  varices  in 
pregnant  women  ; and  hemorrhoids,  to  which  the 
abfence  of  valves  in  the  vena  porta  contributes  much. 
Hence  the  rnenfes  themfelves.  And  when  the  veins 
.return  their  blood  too  flowly  to  the  heart,  the  fubtle 
vapours  being  unable  to  return  from  the  minute  vef- 
fels  to  the  heart,  flagnate  and  occafion  that  fre- 
quency of  cedema  in  weak  people. 

chxxvi.  The  time  in  which  an  ounce  of  blood, 
fent  out  from  the  left  ventricle,  returns  to  the  right, 
and  which  is  commonly  reckoned  the  time  in  which 
the  greater  circulation  is  performed,  is  uncertain, 
and  different  in  every  different  portion  of  the  body. 
If,  however,  you  inquire  concerning  the  ounce  of 
blood,  when  propelled  in  the  quantity  we  have 
mentioned,  with  4500  pulfations,  about  feven  and  a 

half 


ARTERIES. 


8o 


Chap.  \T. 


half  ounces  will  perform  in  an  hour  nearly  twenty- 
three  complpte  circulations  and  a half. 

CLXxvii.  The  effects  of  the  action  of  the  heart 
and  arteries  upon  the  blood,  which  follow  from 
what  has  been  mentioned,  are  various,  and  are  efti- 
mated  by  comparing  the  blood  of  living  vcidi  dead, 
of  healthy  with  difeaied,  and  of  inactive  with  active 
animals.  For  the  blood  of  a Imng  animal  is  warm, 
is  of  a fcariet  colour,  feems  homogeneous,  although 
compofed  of  mixed  principles,  is  entirely  globular, 
flows  very  readily  through  the  molt  minute  veffels, 
and  exhales  the  volatile  halitus,  which  we  have  al- 
ready defcribed  particularly.  In  the  dead  animal, 
before  it  is  tainted  by  putrefaction,  it  lofes  much 
of  its  red  colour  ; it  feparates  into  heavier  and  ligiit- 
fer  principles  ; exhales  no  vapour,  and  when  drawn 
out  from  the  veins,  coUgeals  either  entirely  or  near- 
ly  fa.  But  even  in  living  animals,  when  weak,  in 
which  there  is  fome  pulfe  or  refpiration,  though 
very  fmall,  the  blood  cools  to  a confiderable  de- 
gree. If,  again,  you  compare  the  blood  of  a perfon 
inactive  both  in  body  and  mind,  with  that  of  one 
addidled  to  violent  exercife,  you  will  obferve  in  the 
latter,  a greater  heat,  intenfe  rednels,  greater  com- 
paclnefs,  fpecific  gravity,  and  very  great  abundance 
of  the  volatile  principles.  Ail  which  appearances 
feem  rnanifeftly  the  effects  of  the  action  of  the 
heart  and  arteries,  fmee,  with  its  incrcafe,  they  in- 
creafe,  with  its  diminution,  diminifli,  and  with  its 
ceffation  difappear. 

CLxxviii.  That  we  may  underftand  the  manner  ' 
in  which  thefe  appearances  are  produced  in  the 
blood,  we  muff  confider  what  are  the  effects  of 
the  heart  in  expelling  it,  and  of  the  arteries  in  - 
alternately  comprelling  it.  And,  indeed,  the 
heart  propels  the  blood  with  very  great  velocity 
(cxxiii.)  The  heart  throws  the  blood  into  the 
crooked  arteries,  in  a confufed  manner,  fo  tiut  the 
ri'jrht  ttlobiilcs,  expelled  into  the  mouth  of  the 

aorta. 


Chap.  VI. 


ARTERIES. 


8i 


aorta,  ftrike  againft  the  left  fide  of  the  artery  ^ 
from  whence  being  repelled,  they  incline  towards 
the  right  fide,  and  thus  all  the  particles  of  the 
blood  are  agitated  with  a confufed  and  whirling 
motion.  It  necelfarily  follows,  that  the  blood,  im- 
pelled into  curved  canals,  muft  impinge  on  their 
lides,  dilate  them  and  increafe  their  convexity ; and 
laftly,  in  the  fmalier  veflels,  capable  of  receiving 
but  few  or  only  one  of  the  blood  globules,  in  which 
the  greatefi;  number  or  all  the  globules  come  into 
contact  with  the  fides  of  the  artery,  they  fo  exactly 
rub  againft  them,  that  they  are  even  obliged  to 
change  their  figure  in  order  to  pafs. 

CLXxix.  But  the  arteries,  by  their  elaftic  force, 
repel  the  blood  from  their  fides  towards  the  axis 
of  their  cavities,  and  readl  upon  it  pr effing  againft 
them,  and  laftly  tranfmit  the  globules,  fingly,  into 
arteries  through  the  circular  mouths  of  the  uiti- 

^ O 

mate  feries. 

CLXxx.  In  the  arteries  there  is,  therefore,  a very 
great  degree  of  friction  ; of  the  blood  globules  a- 
gainft  the  arteries  ; of  the  arteries  contracting  round 
the  btood  like  an  obftacle  ; and  of  the  particles  of 
the  blood  amongft  each  other  by  the  confufed  and 
vorticle  manner  in  which  they  are  propelled.  The 
efiedts  of  this  fridtion  are  computed  from  the  vif- 
cid  and  inflammable  nature  of  the  blood,  from  the 
narrownefs  of  the  veflels  through  which  it  runs, 
from  the  ftrong  impulfeof  the  heart, from  the  power- 
ful readtion  of  the  arteries,  and  from  the  weio'ht  of 
the  incumbent  parts  raifed  by  the  force  of  the  arte- 
rial blood.  This  fridlion  generates  fluidity,  by  per- 
petually removing  the  points  of  contadt  between 
its  globules,  refilling  their  force  of  attradlion,  mix- 
ing together  the  particles  of  different  kinds,  which 
become  more  fluid  upon  mixture,  as  in  the  inftance 
of  oil  triturated  with  water.  Then  their  rotation 
and  mutual  attrition  difpofe  the  particles  to  afiume 
a fpherical  figure  j fop  by  breaking  off  their  pro- 
tuberances, 


G 


Al^TERIES. 


Chap.  YT. 


tuberances,  it  renders  tliofe  that  are  ill  formed  or 
branxhy  inore  fphericaL  But  even  the  fragments 
broken  from  the  projecting  furiaces  of  the  ill  formed 
globules,  acquire  a round  iha}?e  from  the  fame  ro- 
tation, attrition,  and  circular  caliber  of  the  minute 
velfels.i-  Hence  blood  coagulates  in  the  vdTels  be- 
fore death  ; and  regains  its  loif  fluidity  by  reftor- 
inp;  the  motion  of  the  heart,  as  are  tauorht  by 
experiments  made  on  li\dng  animals.  Does  the 
motion  of  the  blood,  and  the  denflty  proceeding 
from  it,  produce  the  red  colour,  flnee  it  is  nearly 
in  proportion  to  the  denflty,  and  incrcafes  or  de- 
creafes  from  the  fame  caufes  ? It  feems  to  de- 
pend on  the  calx  of  iron  triturated  with  the  oil. 

CLxxxi.  Does  the  motion  of  the  blood  alfo  gen- 
erate its  heat,  as  in  experiments  with  all  kinds  of 
fluids,  and  even  air,  but  more  efpecially  in  a com- 
buftible  animal  fluid,  denfer  than  water,  com- 
prefi'ed  by  contractile  tubes,  and  rubbed  in  con- 
fequence  of  rapid  inflection  and  extenflon  of 
the  canals  themfelves  ? Is  this  proved  by  the 
blood  belnsc  warm  in  flflies  which  ha^■e  a lar'T;c 
heart,  and  cold  in  thofe  which  have  a fmall  one,  as 
if  the  heat  generated  were  in  the  proportion  of  the 
flze  of  the  heart  to  the  body  ; by  the  great  heat  of 
birds,  whofe  hearts  are  large;  by  the  increafe  of 
heat  by  every  motion,  even  friction  ; by  the  cer- 
tain congelation  of  all  the  human  fluids,  at  a de- 
gree of  cold  in  which  man  freezes  and  retains  his 
blood  warm  as  long  as  he  lives  ; and  by  the  cold- 
nefs  of  perfons  whofe  pulfe  is  weak  and  obfeure  I 
Nor  docs  the  heat  proceed  from  any  incipient  pu- 
trefaction in  the  blood,  flnee  the  fluids,  when  per- 
fe-5lly  at  reft,  do  not  generate  that  degree  of  heat 
nor  is  the  evident  phenomenon  explicable  from  the 
action  of  fuch  an  obfeure  thing  as  the  vital  power  ; 
and  though  fometimes  the  heat  may  be  greater 
when  tlie  pulfe  is  flow,  and  lefs  when  it  is  more- 
frequent,  tlie  difference  may  arile  from  the  differ- 


Cha?.  Vi. 


ARTERIES. 


fent  nature  of  tEe  blood,  from  the  different  den- 
fities  of  the  veffels,  or  from  the  abundance  or  fcan- 
tinefs  of  the  perfpiration. 

CLxxxii.  The  fame  caufe  alfo  checks  putre- 
fadlion,  by  not  fuffering  the  inteftine  motion  to 
be  diminifhed,  by  admixing  antifeptic  pai^ticleSi 
and  by  diffipating  others  which  have  already  be- 
gun to  be  corrupted. 

CLXxxiii.  But  in  confequence  of  the  different 
natures  of  the  particles  themfelves,  which  con- 
jundtiy  conftitute  the  blood,  the  impetus  of  the 
heart  produces  different  effects  on  the  different 
particles  of  the  blood.  Namely,  thofe  particles 
move  more  quickly,  v/hofe  greater  denfity  makes 
them  receive  a greater  impetus,  and  wliofe  apt  fig- 
ure and  lefs  extended  furface  meets  with  lefs  re- 
fiitance  in  the  fluid  in  which  they  move.  Thofe 
alfo  move  more  quickly,  which,  either  from  their 
weight,  or  from  the  direction  in  which  they  pafs 
out  from  the  heart,  move  in  the  axis  of  the  veffeL 
Befides,  thofe  which  have  the  greateft  projeftilc 
motion  vnU  ftrike  asrainft  the  convexities  of  the 
nexures ; while  thofe  which,  from  their  greater 
gravity  or  lentor,  have  lefs  projectile  motion,  will 
move  fluggifhly  along  the  concavity  of  the  veffeL 
In  this  manner  is  the  blood  difpofed  for  the  fe- 
cretions. 

CL XXXIV.  In  the  firft  place,  the  fyfcole  of  the 
arteries  produces  compaftnefs  5 fince,  by  contract- 
ing round  the  blood  as  round  an  obftacle,  they 
comprefs  it  where  vifcid  and  comprefiible,  they 
expel  the  more  liquid  parts  into  the  lateral  mouths^ 
increafe  the  points  of  contact  betwixt  the  globules, 
unite  the  larger,  and  compact  the  flat  particles 
into  denfer  bodies.  But  the  denfity  of  the  blood 
is  partly  as  the  number  of  globules,  and  partly 
as  the  denfity  of  the  fubftance  of  thefe  globules. 

CLXxxv.  Befides,  thefe  very  minute  mouths, 
perviou?  to  one  globule,  feem  to  be  the  meafures 
G a lu 


ARTERIES. 


Chap.  VI. 


8-4 

in  which  the  fanguineous  particles,  being  approxi- 
mated to  a fpherical  figure  by  having  their  points 
rubbed  off,  now  affunie  it  and  become  perfect 
fpheres.  This  is  another  fource  of  denfity,  lince, 
of  all  figures,  the  fphere  is  the  moft  capacious. 

CLxxxvi.  The  anaftomofes  of  the  arteries  re- 
move every  danger  of  obftrucHon,  for  to  any  part 
of  an  artery  where  there  may  be  an  incipient  ob- 
ftruction  or  coagulation  of  the  blood,  they  admit 
an  oppofite  current,  by  which  the  obftacle  is  re- 
pelled in  a contrary  direction  into  a larger  part  of 
the  trunk,  and  is  comminuted  between  it  and  the 
direct  current  of  blood.  The  irremoveable  obftruc- 
tion  or  the  lofs  of  any  veffel,  is  alfo  fuppiied  by  the 
fubfequent  enlargem.ent  of  fome  contiguous  branch, 
as  is  proved  by  furgical  fa<Ts,  in  which  the  princi- 
pal artery  has  been  cut  or  tied.  The  collilion  of 
thefe  oppofite  torrents  of  blood  takes  fomething 
f rom  its  velocity  ; and  the  reticular  diftribution 
augments  the  friction  of  the  globules. 

CLXx^cvii.  In  like  manner  as  the  velocity,  fothc 
flow  motion  of  the  blood  in  the  ultimate  velfels  Las 
its  peculiar  effects.  In  the  larger  arteries,  the  m.oft 
heterogeneous  particles  are  whirled  about  amongft 
each  other  ; in  the  fmaller  branches,  the  progref- 
live  motion  of  the  blood  being  diminiflied,  the 
lighter  particles  feparate  from  the  very  ponderous 
and  red  globules,  and  are  forced  towards  the  cir- 
cumference and  branches,  while  the  compact  glo- 
bules rem.ain  in  the  axis.  The  attraftive  powers 
of  the  particles  of  the  blood  are  alfo  increafed  ; 
hence,  the  oily  particles  which  are  both  fluggifli 
and  large,  attract  each  other,  and  feparate  by  open 
lateral  mouths ; and  other  thinner  fluids  are  lent 
off  through  lateral  branches  of  a fmaller  orifiee,  till 
at  length  little  more  than  the  red  blood  alone  pafl- 
es  into  the  incipient  vein.  Heterogeneous  particles 
arc  alfo  mixed  in  a Angle  vein,  that  the  blood  may 
be  prepared  for  certain  ufes,  as  in  the.  vena  porta- 

rum. 


Chap. 


SECRETION. 


^5 

rum.  But  all  thefe  particulars  which  prepare  the 
blood  for  the  fecretions,  we  lhall  conlider  in  the 
following  chapter. 

CHAP.  VII. 

SECRETION. 

CLXXxviii.  ^ I '’HE  fluids  which,  being  depofited 
§ from  the  blood  into  other  veflels, 
are  faid  to  be  fecreted,  feem  reducible  to  four  clalT- 
es.  The  jirjl  confifts  of  vifcid  fluids,  coagulable 
by  a heat  of  about  150  degrees,  by  alcohol,  and  by 
ftrong  acids  ; although  generally,  in  the  living  ani- 
mal, they  efcape  in  the  form  of  vapour,  and  after 
death  are  compared  into  a gelatinous  fubftance. 
To  this  clafs  belong  the  liquor  and  halitus  of  the 
ventricles  of  the  brain,  of  the  pericardium,  pleura, 
peritoneum,  tunica  vaginalis,  amnois,  joints,  renal 
capfules,  and  probably  of  the  womb,  with  the  juices 
of  the  ftomach  and  inteftines,  and  laftly  the  lymph 
generally  known. 

CLXxxix.  The  fccond  clafs  confifts  of  fluids,  of 
which  fome,  in  like  manner,  are  exhaled,  but 
more  Ample  than  the  former  (clxxxviii.)  and 
more  aqueous,  are  not  coagulable  by  fire  or  by  fpir- 
its  of  wine ; and  others  are  not  exhaled,  but,  being 
depofited  in  their  refpedtive  excretory  ducts,  are 
excreted  in  their  proper  places  by  the  common  out- 
let of  fome  gland.  To  the  former  of  this  clafs  be- 
long the  perfpirable  matter  of  Sanftorius,  part  of 
the  tears,  and  the  v/atery  humour  of  the  eye.  To 
the  latter  of  this  clafs  belong  the  remaining 
part  of  the  tears,  the  faliva,  pancreatic  juice, 
and  the  urine.  The  fweat  feems  to  be  a mix- 
ture of  the  perfpirable  matter  and  the  fubcuta- 
neous  oil. 


cxc. 


86 


SECRETION. 


Chap.  YIL 


cxc.  The  third  clafs  differs  from  both  the  pre- 
ceding, being  heavier  than  water,  fluggilh  and 
vifcid,  but  of  an  aqueous  nature,  not  congealable 
into  a jelly,  but  hardening  into  dry  crufts  by  ex- 
haling their  water.  Thole  do  not  eflervefce  with 
any  fait,  but  are  contracted  and  made  thicker  by 
acids.  By  lixivial  falts  they  are  diflblved.  By  fire 
they  are  refolved  into  water,  a little  volatile  fait, 
and  a little  oil.  Of  this  kind  are  the  whole  mucus- 
in  the  human  body,  extended  over  all  the  internal 
pafiages  for  air,  aliments,  or  urine,  and  the  cavities 
of  the  genital  parts  ; and  femen. 

cxc  I.  The  clafs  is  that  of  the  inftammable 
juices,  which,  when  recent,  are  indeed  thin  'and 
Vv^atery,  but,  byftagnation  and  by  evaporatmg  their 
water,  become  thick,  oily,  inflammable,  and  often 
bitter  liniments.  To  this  clafs  we  refer  the  bile,, 
earWax,  tallovc,  the  oily  liniment  of  the  fkin,  the 
marrow  in  the  bones,  and  all  the  fat  throughout 
the  human  body ; and  caftor,  and  the  yolk  of  the 
egg.  The  milk  itfelf,  fo  far  as  it  contains  butter, 
belongs  to  this  clafs. 

cxcii.  Other  humiours  are  compounded  of  thefe 
which  we  have  deferibed  as  Ample  ; as  the  mik,  of 
butter  and  water  ; and  the  liniment  of  the  joints,  of 
lymph  and  fat. 

cxciii.  Whoever  confiders,  that  in  the  blood  are 
found  a coagulable  ferum  (^cxxxvii.)  an  exhaling 
water  (cxi.ii.)  a fort  of  vikid  mucus  (cxxxviii.) 
and  iaftly  an  oil  (cxlii.)  wiU  begin  to  perceive 
the  perfecl  poflibility  of  the  foregoing  clafl'es 
(cLxxxviii.  to  cxci.)  of  humours  being  feparated 
from  the  blood,  fince  their  principles  exift  in  the 
fanguineous  mafs.  But  in  what  manner  it  is  brought 
about,  that  oil  is  feparated  from  the  blood  in  one 
part,  water  in  another,  and  mucus  in  a third,  re- 
mains to  be  explained,  and  requires  a defeription 
of  tlie  fccretorv  organs. 


QXCIV, 


Chap.  Ylt 


SECRETION. 


7 


cxciv.  The  coagulable  juices  are  feparated  al- 
moft  every  where,  from  the  arteries  themfeives,  in- 
to excretory  canals,  continuous  with  the  arteries, 
without  any  intermediate  organ.  The  proof  of  this 
we  have  from  injections  of  glue,  water,  and  thin 
oils,  which  very  readily  exude  from  the  red  arte- 
ries, and  are  poured  out  into  all  the  cavities  in  which 
that  coagulable  vapour  is  naturally  found,  with- 
out meeting  vdth  any  intermediate  knots  or  retard- 
ing cells.  Finally,  the  blood  itfelf,  being  poured  out 
into  moft  of  thefe  .cavities,  without  any  permanent 
kfion,  in  confequence  of  ftagnation,  retardation, 
or  fmall  increafe  of  impetus,  Ihows  plainly  that  the 
paffage  betwixt  the  red  blood-veffels  and  thofe  ex- 
cretory du<Ts  is  neither  long  nor  difficult,  and  that 
the  yellow  ferum  does  not  differ  much  from  blood. 

cxcv.  Another  liquid,  coagulable  by  acid  fpirits 
and  alcohol,  is  the  albuminous  humour  of  the  joints, 
w'hich  being  compofed  of  fat,  medullary  oil,  and 
watery  exhalation,  ccnfiitutes  an  exceedingly  foft 
liniment,  very  fit  for  lubricating  the  cartilages,  and 
leffening  friction.  For  fecreting  this,  there  are  def- 
tined  certain  conglomerate  glands  of  a peculiar 
ftructure,  which  are  fo  fituated  in  the  rough  pits  of 
the  articulations  of  the  bones,  that  they  may  be 
moderately  compreffed,  but  cannot  be  crufhed. 

cxcvi.  The  ftrufture  of  thefe  glands  is  peculiar. 
The  larger  cluflers  of  glandular  acini  adhere,  for 
the  molt  part,  to  the  bone  by  a broad  bafis  wrap- 
ped up  in  fat.  Thence,  being  extenuated  into  a 
crefted  edge,  they  pour  out  their  liquor  from  an  ex- 
ceedingly thin  border,  by  open  ducts,  which  how- 
ever I do  not  find  very  evident.  Other  fmaller 
ones,  placed  every  where  in  the  capfules  of  the  ten- 
dons, and  between  the  diverging  fibres  of  the  liga- 
mentary  capfules  of  the  joints,  feem  to  be  ahnoft  of 
the  nature  of  fimple  glands,  and  are  turgid  with 
yellow  mucous  ferum. 


'CXCVII, 


88 


SECRETION. 


Cfup.  ■^TI, 


cxcvii.  The  imcoagulable  juices  (clxxxix.)  of 
the  firft  fort  are  fecreted  in  the  fame  manner  ^vnth 
the  coagulable  ones  (clxxxviii.)  to  wit,  from  ex- 
haling arteries,  which  arife  from  the  red  arteries, 
without  any  intermediate  follicle.  In  the  velfcls, 
which  exhale  the  cutaneous  perfpiration,  and  in 
the  lachrymal  veiTeis  of  the  firft  fort  having  a wa- 
tery ftuid ; injections  of  water,  or  thin  fize  exude 
from  the  arteries,  fo  as  to  remove  every  doubt  of 
this.  Thefe  arteries  are  alfo  irritable,  fo  that,  from 
the  contact  of  an  acrid  fubftance,  they  difcharge 
more  juice  in  a given  time,  than  in  a ftate  of  health. 

cxcviii.  But  in  the  latter  kind,  the  falival,  the 
fecretion  is  made  by  means  of  conglomerate  glands, 
which  the  ancients  firft  diftinguifiied  by  their  cluf- 
ter  like  fabric,  and  efteemed  glands.  Thefe  are 
compofed  of  acini  or  roundifh  lobules,  conjoined 
together  into  a larger  mafs,  by  loofe  cellular  fub- 
ftance, which  is  often  covered  externally  by  fome 
denfe  cellular  membrane,  as  a common  envelope, 
as  in  the  parotid  and  maxiUary  glands.  Through 
the  intervals,  betwixt  the  clufters,  run  the  arteries 
vchich  are  here  pretty  large,  and  the  veins.  But 
moft  of  the  conglomerate  glands  feparate  their 
fiuids  from  the  blood,  and  difcharge  it  in  the  fol- 
lowing manner  : Each  acinus  fends  out  an  excre- 
tory duel,  which  ioins  with  others  of  the  fame  kind, 
into  a larger  trunk,  forming  at  laft,  in  the  manner 
of  veins,  one  canal,  which  conveys  the  humour, 
feparated  by  the  gland,  to  the  part  for  which  it  is 
defigned,  as  the  cavity  of  the  mouth,  inteftines,  fur- 
face  of  the  eyes,  &c.  There  are,  indeed,  fome  in- 
ftanccs  in  which  either  there  are  no  excretory 
durfts,  or  they  have  not  hitherto  been  diicovered  ; 
as  the  thyroid  gland,  capfuls  renales,  and  thymus, 
unlefs  thefe  approach  to  the  nature  of  conglobate 
crlands. 


CXCIX.  1 
lilvjted  by 


he  acini  themfelves  are  furreunded  and 
fome  firm  cellular  fubftance  3 and  are 


Chap.  VII. 


SECRETION. 


89 

alfo  fubdivided  into  leffer  acinuli,  as  is  evident  to 
the  eye,  and  by  tlie  microfcope.  How  does  this 
fubdivilion  end  ? Is  every  fimpie  acinus  hollow  in 
its  middle,  receiving  the  humour  tranfuding  from 
the  arteries  in  a follicle,  and  fending  it  out  by  an 
excretory  duft  ? Is  this  ftruclure  rendered  probable 
by  eruptions,  hydatids,  and  the  kidneys  filled  with 
round  fchirri  ? Are  the  larger  vifcera,  appointed 
for  fecretion,  conglomerated  glands  ? Is  this  opin- 
ion made  probable  from  the  morbid  round  concre- 
tions formed  in  the  liver,  fpleen,  kidneys,  tefticles, 
and  cortical  fubftance  of  the  brain  ; or  from  the 
bunch  like  appearance  which  thofe  vifcera  have  in 
fmailer  animals  ? In  the  cellular  fubftance  that  fur- 
rounds  every  part  of  the  human  body,  even  the 
extreme  vafcules,  are  there  hollow  fpaces  and  cells, 
into  which  a fecreted  humour  is  poured  ? 

cc.  Nothing  of  this  kind  feems  to  be  the  cafe. 
For,  indeed,  the  acini  compofing  the  vifcera  of  ani- 
mals, are  .not  elementary,  but  compofite  lobes,  and 
large  in  proportion  to  the  animals.  The  morbid 
concretions  are  almoft  all  of  them  feated  in  the  cel- 
lular fubftance,  and  in  the  limbs  themfelves,  where 
there  is  not  the  leaft  room  to  fufpecl  any  thing  of 
a glandular  fabric  ; and  are  compofed  of  oil,  earth, 
and  vaporous  particles,  extravafated  into  fome  of  the 
cellular  cavities,  where,  ftagnating  and  compreliing 
the  adjacent  foUicles,  they  form  to  themfelves  proper 
membranous  tunics,  Befides,  the  watery  and  fluid 
nature,  of  the  juice  fecreted  in  thefeglands  (clxxxix.) 
is  an  argument  that,  during  its  fecretion,  it  met 
with  no  retardation,  no  place  in  which  it  ftagnated. 
For  the  fluids  ‘which  remain  at  reft  in  the  warm 
cavities  of  the  human  body,  which  are  full  of  ab- 
forbing  vefiels,  are  all  .infpilTated,  and  approach, 
either  towards  a mucous  or  an  oily  nature.  More- 
over, anatomical  injections  would  meet  with  more 
difficulty  in  paffing  from  the  arteries  into  the  ex- 
cretory ducts } which  would  be  impervious  to  thick 
' injections. 


SECRETION. 


Chap. 


injections,  and  tliiii  ones  would  be  exhaled  into  the 
cellular  fubftance.  Yet  we  fee,  that  the  fuperiative 
art  of  great  anatomifts  has  conveyed  thick  injec- 
tions, like  wax,  directly  from  the  arteries  of  the 
falivary  glands,  liver,  &c.  into  continuous  excretory 
dufts ; and  this  without  filling  up  any  intermediate 
cavities,  which,  according  to  the  foregoing  hypo- 
thefis  (cxcix.)  fhould  happen. 

cci.  Therefore,  the  acini  appear  to  be  compofed 
of  arteries  and  veins,  divided  and  fubdivided,  part- 
ed and  connected  by  the  intervention  of  a good 
deal  of  cellular  fubftance,  which,  becoming  gi'adual- 
ly  more  compact,  alfumes  a fpheroidal  figure.  Tliis 
is  fupported,  by  analogy  in  the  lobes  of  the  lungs, 
in  the  lobules  of  the  thymus,  in  the  ftnicture  of  in- 
fects ; but  more  efpecially  in  the  tefticle,  of  which 
the  lobules  are  evidently  formed  of  excretory  dueds, 
connected  together  into  fafciculi  by  a very  foft 
membrane.  The  glands  do  not  feem  to  pour  their 
fluids  into  cellular  fubftance,  as  by  it  the  paflage  to 
the  excretory  ducts  would  be  obftructed  or  prevent- 
ed. The  induftry  of  anatomifts  has  lately  difeovered 
very  fmall,  white,  cylindric  veffels,  the  real  elements 
of  the  vifeera ; and  it  is  to  be  hoped  that  this  dif- 
covery  will  be  confirmed  by  future  obfervations. 

cell.  Thin  fluids,  neither  coagulable  nor  exhal- 
ing, but  aqueous,  are  likewife  generated  in  other 
parts,  without  the  affiftance  of  conglomerate  aci- 
nous glands.  Thus,  the  urine  is  depofited  from 
the  red  arteries  into  membranous  tubes,  manifeftly 
continuous,  in  a manner  which  readily  admits  the 
paflage  of  air,  water,  or  mercury.  The  nervous 
fluid  feems  to  be  fecrcted  in  the  brain,  in  a fimilar, 
though  lefs  apparent  manner. 

cciii.  The  third  clafs  of  fluids,  the  mucous,  (cxc.) 
is  almoft  every  where  fecreted  from  fmufes  or  liol- 
lovr  glands.  The  ftruchire  of  true  glands  or  folli- 
cles, in  general,  confifts  of  an  ample  cavity,  every 
wll$re  circumfci'ibcd  by  a membrane  ■,  but  in  fuch 

a mamier, 


Chap.  VII. 


SECRETION. 


9* 

a manner,  that  the  flefli  itfelf  of  the  part,  to  which, 
the  gland  adheres,  ioraetimes  forms,  the  one  fide, 
and  completes  the  hemilphere  of  the  follicle.  In 
other  places,  a continued  membrane  forms  the  whole 
of  the  round  or  oval  receptacle  of  the  gland.  The 
cavity  is  in  general  round  ; but  fometimes  it  is  ob- 
long, and  lituated  obliquely  betwixt  the  adjacent 
parts  ; as,  for  example,  in  the  urethra  of  the  male, 
and  in  the  foUicles  of  the  linus  muliebris.  They 
are  irritable  ; and,  v/hen  ftimukted  by  acrid  fub- 
liances,  accelerate  their  fecretions. 

cciv.  Into  thefe  follicles  minute  arteries,  either 
from  the  flefli  in  which  it  is  feated,  or  from  the 
membrane  ivhich  conftitutes  its  convex  fide,  open 
by  extremities  extended  into  the  cavity  of  each 
crypta,  into  which  they  pour  their  refpeTive  juice ; 
after  being  received  into  the  follicle,  it  is  detained 
from  the  narrownefs  of  the  excretory  duff,  and 
infpiflated,  the  more  watery  parts  being  abforbed 
by  the  veins,  which  correfpond  to  the  exhaling  ar- 
teries. The  truth  of  this  we  are  taught  from  the 
ftrufture  of  the  Ample  follicles  obfervable  in  the 
tongue,  in  which  both  the  importing  pores,  and  the 
excretory  ducts,  are  even  vifible  to  the  eye  ; and 
from  the  tubuli  of  the  ftomach  of  birds,  in  which 
the  fecreting  villi  manifeftly  protrude  into  the  cav-. 
ity  ; and  laftly,  from  injeftions,  which  force  wax 
colourlefs  into  the  Ample  glands. 

ccv.  The  long  mucous  Anufes,  and  round 
glands,  are  both  furniflied  with  excretory  duffs, 
which,  for  the  moA  part,  are  fulAciently  large  ; al- 
though, in  the  round  glands,  they  bear  no  great 
proportion  to  the  cavity  of  the  gland,  Thefe  ori- 
fices often  open  into  the  common  large  cavity,  into 
which  the  mucus  is  poured,  without  any  interme- 
diate duff;  as  in  the  back  of  the  tongue,  and  in 
the  Ample  glands  of  the  ftomach  and  inteftines. 
Thefe  have  been  denominated  cryptae  by  Ruyfcli.. 
The  Anufes  have  pfcen  a Amilar  ftruffure,  and, 

open. 


SECRETION. 


9^ 


Chap.  \TI. 


open,  without  an  intervening  duel,  as  in  the  ure- 
thra of  the  male, 

ccvi.  In  another  kind  of  thefe  glands,  there 
are  many  limple  follicles  contained  in  one  common 
covering,  which  open  with  ample  orifices  into  one 
common  finus,  without  any  true  excretory  duct, 
as  in  the  tonfils.  Thefe  are  called  conglutinated 
glands.  < 

ccvii.  Other  Ample  glands  have  an  excretoiy 
duct,  by  -which  they  excrete  their  mucus  ; namely, 
a membranous,  cylindric,  narrow  veffel,  opening 
with  its  pofterior  orifice  into  the  cavity  of  the 
gland,  and  with  its  anterior  orifice  into  the  com- 
mon cavity  for  which  its  mucus  is  defigned.  Thefe 
excretory  du£ls  are  of  confiderable  length  in  the 
fubcutaneous  and  febaceous  glands,  and  in  thofe  of 
the  palate  and  windpipe.  In  fome  parts,  the  pore 
and  duct  are  more  eafily  demonftrable  than  the  fol- 
licle, as  in  the  noftrils,  larynx,  reclum,  &c. 

ccviii. . In  other  places,  feveral  of  thefe  duds, 
arifing  each  from  its  refpedive  follicle,  run  togeth- 
er like  the  branches  of  a vein,  fo  as  to  form  one 
confiderable  excretory  canal,  com.inon  to  a number 
of  follicles.  To  this  kind  belong  the  compound 
glands  of  the  inteftines,  and  the  blind  finus  at  the 
root  of  the  tongue,  of  the  clafs  of  glands  ; and  of 
the  finufes,  fome  compound  finufes  of  the  urethra, 
and  the  tubulous  fibres  of  the  ftomachs  of  filhes 
and  of  birds.  Glands  of  this  fort  may  be  faid  to 
he  compounded  of  Ample  ones  ; but  where  they  lie 
only  contiguous,  they  may  be  called  aggregate  or 
congregated  glands  ; as  are  thofe  of  the  tauces,  fto- 
mach,  inteftines.  See. 

ccix.  The  inflammable  juices  (cxcix.)  are  fepa- 
rated  by  organs  diftering  in  their  fabric.  The  fat 
and  marrou'^  are  depofited  into  cellular  fubftance, 
without  the  intervention  of  ^ands,  from  the  finall 
mouths  of  the  arteries.  The  fubcutaneous  fat 
every  where  exudes  through  fmall  duels  and  pores, 

\t'ithout 


Chap,  VII. 


SECRETION. 


93 

without  any  glandular  follicles.  - But  the  -earw2LX 
and  cutaneous  fuet  are  fecreted  by  glands  of  differ- 
ent kinds.  Many  of  the  febaceous  glan,ds  are  vifi- 
ble,  \Auth  a naked  mouth  in  the  ficin,  and  without 
a duel  of  any  length ; as  we  fee  in  the  ears,  ai'eolac 
of  the  nipples,  in  the  female  nymphse,  and  the 
groove  betwixt  them  and  the  labia,  and  in  the  pre- 
puce of  the  penis  and  clitoris.  Thefe  differ  but 
little  from  the  cryptse  (ccv.)  except  in  the  matter 
which  they  fecrete. 

ccx.  There  are  others  of  the  febaceous  glands^ 
W'hich  have  an  excretory  du6l  of  fome  length  ^ as 
almofl  ail  the  cutaneous  ones,  which,  being  feated 
in  the  cellular  fubfcance,  are  neceffarily  prowded 
with  a dudl  to  perforate  the  Ikin.  This  is  moll 
evident  in  the  face,  where  the  length  of  the  duel  is 
indicated  by  maggot  like  fubflance  preffed  out ; 
the  bulk  of  which  demonftrates,  that  a follicle  lies 
under  the  flender  pore. 

ccxi.  There  are  hill  other  febaceous  glands  of 
the  kind,  mentioned  ccviii.  in  which  the  fmail 
du(ils  of  many  cryptse  meet  together  in  one  larger 
excretory  du6l.  Thus,  in  the  face,  in  feveral  places, 
the  large  pores  are  in  common  to  a number  of 
cryptae.  Of  this  kind,  alfo,  are  thofe  febaceous 
du(Ts  in  the  eyelids  ; and  the  unguinous  glands  in 
the  fecretory  organ  of  the  mufk-goat,  beaver,  hy- 
aena, civet-cat,  and  mufk-rat,  which  pour  their  fe- 
baceous matter  into  one  common  receptacle. 

ccxii.  The  milk,  which  is  compofed  of  water 
and  oil,  and  perhaps  of  abforbed  fat,  and  is  a fluid 
of  a peculiar  nature,  is  fecreted  in  a conglomerate 
gland,  fuch  as  we  deferibed  at  cxcviii.  The  bile 
is  a matter  of  controverfy ; but  there  are  many  ar- 
guments in  favour  of  the  vafcular  flruclure,  and  of 
the  bile  being  depofited  in  the  pori  biliarii,  from  the 
vena  portarum,  without  intermediate  follicles;  efpe- 
cially  the  Ruyfehian  art  of  inje<5lion,  in  which  the 
wax  paffes  dire^iy  from  the  porta  into  the  biliary 

pores. 


SEC^ETIOl'^. 


Chap.  \1L 


§4 

pores,  witliout  meeting  with  any  intermediate  knots 
retarding  it.  The  milk  and  bile  are  both  of  them 
however  much  thinner,  and  more  watery,  than  the 
fat,  or  the  febaceous  m.atter  in  follicles. 

ccxiii.  It  remains  for  us  to  inquire,  how  it  hap- 
pens, that  from  one  common  mafs  of  the  blood,  the 
fame  variety  of  peculiar  fluids  are  conftantly  fepa- 
rated,  each  in  its  refpective  place,  and  that  milk  is 
never  ferreted  in  the  kidneys,  bile  in  the  thymus, 
or  mucus  in  the  febaceous  glands.  This  problem 
will  be  at  laft  perfe<5fly  folved  by  one  who  lhall  be 
intimately  acquainted  with  the  internal  ftruchire 
of  the  fecreting  organs.  In  the  mean  time,  I fliall 
notice  what  is  hitherto  known  with  fulHcient  cer- 
tainty. 

ccxiv.  In  the  firfl:  place,  the  blood  itfelf,  from 
which  any  liquid  is  to  be  fecreted,  aflumes  in  vari- 
ous places,  that  peculiarity  of  character,  that  it  con- 
tains more  particles,  of  a like  nature  with  thofe 
which  nature  wilhes  to  predominate  in  the  fluid  to 
be  fecreted.  In  the  liver,  the  venous  blood  arrives 
witli  a flow  motion,  loaded  with  oil,  and  the  femi- 
putrid  vapours  of  the  inteftines.  To  the  tefticles, 
the  blood  is  brought  flowly,  through  long,  {lender 
and  inflected  canals,  arifing  at  very  fmall  angles, 
under  the  ikin,  in  a cold  fltuation.  In  the  carotids, 
it  is  probable  that  the  ftronger,  fpirituous,  and  denfe 
parts  of  the  blood  afeend  ; fo  that  that  is  more  wa- 
tery, which  defeends  into  the  abdomen  and  to  the 
kidneys,  and  forms  the  faliva  of  the  pancreas,  and 
the  gaftric  and  inteftinal  juices. 

eexv.  Befidcs,  the  blood  is  prepared  for  fecre- 
tion,  by  its  retardation  in  the  minute  velfels,  in  con- 
fequence  of  which,  the  red  and  denfer  parts  alone 
occupy  the  axis  of  the  canal ; while  the  other. light- 
er, m.ore  iluggifh,  and  lefs  quickly  moved  particles, 
recede  to  the  lateral  branches,  impinge  on  the  iecre- 
tory  mouths  ariiing  from  the  fldes  of  th.e  veliels, 
and  adhere  to  them  by  their  vifcofity. 


ccxyi. 


Chap.  VII.  SECRETION.  9^ 

ccxvi.  Thefe  orifices,  though  poffibly  of  dif- 
ferent diameters,  are  always  too  fmall  to  admit  the 
lalood  in  their  natural  ftate.  As  from  an  increaf- 
ed  aclion  of  the  heart,  many  of  them  admit  blood, 
we  may  conclude,  with  probability,  that  they  arife 
continuous  with  the  red  arteries,  and  are  not  much 
fmaller  than  the  red  globules.  Hence  the  fame 
fecretory  orifices  refufe  thick  injeftions  of  wax  or 
fuet,  and  generally  admit  thinner  liquors  injected 
into  the  arteries.  Therefore,  this  is  the  firft  and 
mod;  hmple  mechanifm  of  fecretion,  viz.  that  the 
caliber  of  the  excretory  ducd  admits  only  thofe  par- 
tides,  of  which  the  greateft  diameter  is  lefs  than 
the  diam.eter  of  the  duct.  It  is  only  in  this  way 
that  the  yellow  arteries  convey  a pure  liquor  from 
the  blood,  and  that  the  uriniferous  dudls  exclude 
the  red  blood  and  coagulable  ferum.  But  this  is  not 
the  foie  caufe,  fince  limilar  fluids  are  generated  by 
large,  as  well  as  by  fmall  animals. 

cGxvii.  Merely  according  to  this  law,  the  fecret- 
ed  juices  may  be  of  many  different  kinds : for  the 
very  minute  orifices  will  only  admit  fluids  of  ex- 
treme tenuity,  as  in  the  fmall  veflels  of  the  brain ; 
while  the  larger  will  admit  water  and  jelly  ; and 
tlie  largeft  of  all,  fat.  Moreover,  if  a number  of 
fecretory  organs  arife,  in  fucceflion  from  one  fecern- 
ing  artery,  and  be  provided  with  large  orifices,  thofe 
which  arife  laft  from  the  artery  will  admit  only 
the  thinneft  fluids.  If,  on  the  contrary,  thofe  which 
arife  firft  in  order  from  the  fecreting  artery,  be 
fmail,  the  laft  ones  v/ill  receive  only  the  groffer  li- 
quids. It  may  be  objefled,  that  though  the  veflels 
in  the  foetus  are  vaftly  lefs  than  in  an  adult,  yet  the 
humours  are  the  fame.  But  thefe  humours,  which 
are  called  fat,  bile,  lymph,  and  urine,  in  the  foetus, 
are  very  different  from  the  fat,  bile,  lymph,  and 
urine  of  an  adult. 

ccxviii.  It  is  altogether  in  this  way,  that  moft 
fecrctions  are  made  by  veflels  ajiflng  immediately 

from 


SECRETION. 


Chap.  VIL 


g6 

from  fangiiiferous  arteries  (xlv.)  Thefe  feparate 
grofs  juices ; thick,  coagulable,  or  watery  j as  the 
fat,  urine,  juice  of  the  ftomach  and  inteifines,  &;c. 
But  other  fecretions  of  thinner  juices  are  perform* 
cd  by  veflels  ariling  from  the  inferior  orders  of  ar- 
teries, not  fanguiferous  ; to  the  orifices  of  which, 
not  only  no  red  blood,  but  no  ferum,  fat,  or  other 
grofs  fluids,  can  have  admittance.  Thus  the  more 
thin  and  pure  humours  muft  neceflarily  be  feparat- 
ed  ; as,  for  example,  in  the  eye. 

ccxix.  Perhaps  the  angle,  which  the  fecretory 
branch  forms  with  its  trunk,  contributes  fom.ething 
to  fecretion.  For  it  is  eafily  demonftrated,  that 
at  right  and  reflefted  angles,  only  the  \dfcid  and 
fluggifh  juices  are  expelled,  in  confequence  of  the 
ftronger  force  of  the  particles  keeping  the  middle 
of  the  canal  ; and  that  the  liquids  which  prefervc 
their  velocity,  are  thofe  fent  off  at  acute  angles. 
For  men  of  credit  have  obfcrved,  that,  in  liwing 
animals,  the  velocity  is  greater  in  acute  angles, 
and  lefs  in  right  angles.  The  very  ftruclure  of 
the  body  convinces  us,  that  thefe  angles  have 
fomie  effect  on  fecretion,  fincc  in  difl'erent  parts  we 
find  the  angles  at  which  the  branches  proceed  from 
the  trunks  different,  and  the  reticulations  different. 
For  the  ultimate  veffels  are,  in  general,  arbufcular, 
the  trunks  fending  out  branches  on  eveiy  fide,  but 
at  difierent  angles  ; thus,  at  fmall  angles  in  the 
larsre  inteflines,  and  lar2;e  antrles  in  the  fmall  in- 
teftines.  Thus  in  the  fpleen,  the  fmallcr  red  arte- 
ries arife  fo  tlnck  from  tlieir  trunks,  that  theyre- 
femble  a fprinkler ; in  the  inteflines,  they  refemblc 
pencil  brufhes  ; in  the  kidneys  they  are  ferpentine  ; 
in  the  liver  radiated ; in  the  tefticle,  they  are  curl- 
ed up  like  a lock  of  hair  ; and  in  the  uvea  they  arc 
anular.  But  it  is  no  improbable  conjecture,  that 
the  Creator  never  made  this  diverfity  of  fabric  in 
vain.  "VVe  have  not  as  yet,  however,  any  account  of 
thefe  reticulations  that  is  fulEciently  accurate  ; nor 

docs 


Chap.  VII. 


SECRETION. 


97 

does  a fimilarity  in  the  fluids  fecreted  feem  to  be 
connefted  with  a fimilarity  of  ftrufture.  The  veins 
too  have  fimilar  reticulations,  for  the  purpofe  of  fa- 
cilitating the  motion  of  the  blood,  and  not  for  di- 
verfifying  the  nature  of  the  fecretions. 

ccxx.  The  inflexions  of  the  fmaller  veiTels,  as 
well  arteries  as  excretories,  greatly  retard  the  mo- 
tion of  the  blood ; in  which  the  greater  part  of  the 
force  received  from  the  heart  is  evidently  fpent  in 
the  change  of  figure  in  the  veflel.  The  repeated 
inflexions,  therefore,  of  the  fecretory  arteries  colleX 
the  vifcid  parts  of  the  fluids,  by  giving  them  time 
to  attraX  each  other.  A ftrais^ht  courfe  of  the  vef- 
lels  is  favourable  to  celerity  of  motion,  rendering 
the  fecretion  copious  and  eafy,  but  impure,  as  we 
fee  in  the  urine. 

ccxxi.  That  the  ultimate  arteries,  and  in  like 
manner  the  fecretory  orifices,  have  different  degrees 
of  denfity,  is  not  improbable,  fince  we  aXually  find 
it  fo  by  experiments  in  the  larger  branches.  But 
the  denfer  the  capillary  arteries  are,  the  more  will 
they  adm.it  only  the  ftrong,  and  at  the  fame  time 
minute  particles,  and  exclude  thofe  that  are  lighter, 
moved  with  lefs  velocity,  and  groffer.  Irritability 
produces  almoft  the  fame  effeXs  j for  if  the  fecre- 
tory orifice  be  irritated,  it  will  rejeX  the  grofs  hu- 
mours, and  tranfmit  the  more  fluid  ones  : inftead 
of  mucus  in  the  urethra,  it  will  feparate  a thin  yel- 
low ferum  ; and  a fimilar  fluid,  inftead  of  the  fub- 
cutaneous  fat : the  quantity  of  fecreted  liquor  will 
alfo  be  increafed  ; as,  for  example,  in  the  tears. 

CCXXI  I.  Laftly,  the  velocity  is  greatly  increafed,  if 
the  heart  be  near,  if  the  artery  be  ftraight,  if  it  go  off 
at  a fmall  angle,  or  if  the  excretory  duX  arife  near 
the  extremity  of  a confiderable  arterial  branch. 
The  velocity  is  diminifhed,  if  the  fecreting  artery 
run  a long  way  capillary,  loofing  the  greater  part  of 
the  motion  of  its  blood,  from  friXion,  if  it  arife  at 
a diftance  from  the  heart,  and  at  a large  angle. 

H Finally, 


SECRETION. 


Chap.  VR. 


Finally,  from  whatever  caufe  the  dlverhty  may  pro- 
ceed, an  increafe  of  velocity  increafes  the  quantity  of 
fluid  fecreted,  carries  off  the  heavy  liquids,  and  ren- 
ders the  fecretions  thicker  and  more  impure,  though 
fluid,  as  it  prevents  llagnation,  by  which  they  con- 
tract vifcidity  ; but  flownefs  facilitates  attraction 
and  vifcidity,  and  renders  the  fecreted  juice  more 
pure  ; as  the  fimilar  particles,  when  brought  togeth- 
er, can  better  attraft  and  join  each  other,  under  a 
flow  motion,  fo  as  to  retain  the  larger  canal,  while 
the  thinner  parts  go  off  by  the  leffer  lateral  branch- 
es. Hence,  from  the  impetus  of  the  heart  alone 
being  too  much  increafed,  all  the  fecretions  become 
confounded. 

ccxxiii.  Thefe  conditions,  nature  is  able  vari- 
oufly  to  unite  or  feparate,  and  to  impart  to  each  or- 
gan, in  greater  or  lefs  degrees ; and  thus,  to  modi- 
fy the  fecreted  humours  in  various  vuys.  Anat- 
omy furnifhes  examples,  if  you  compare  the  fecret- 
ing  apparatus  of  the  bile  or  femen,  which  are  thick 
juices,  v/ith  thofe  of  the  urine  and  tears,  whicli  are 
fluid  ones, 

ccxxiv.  From  all  that  has  been  advanced,  we 
may  perceive,  that,  fince  the  blood  contains  parti- 
cles of  various  kinds  ; tome  fluggifla  and  mucous  j 
fome  coagulable,  but  fluid  ; fome  denfe  and  red  ; 
fome  watery  and  thin  ; and  others  fat  and  aufeid 
(cLxxxviii,  et  fcq.')  among  all  thefe  particles,  thofe 
which  are  the  iai'geft  and  moll  denfe,  fuch  as  the 
cruor,  will  continue  in  the  axis  of  the  veffel,  and 
in  the  trunk,  fo  as  to  pafs  on  in  a continued  courfe 
into  the  fanguiferous  vein  (xxxix.) 

ccxxv.  Ihofe  particles  which  are  grofs  and  fiug- 
gifh,  fuch  as  the  fat,  muft  go  off  by  the  larger  ori- 
fices ariling  laterally  from  the  fanguineous  arter^g 
by  fhort  dufts  ; for  in  long  dufts  the  oil  would 
ftagnate,  from  its  fluggiflmels.  The  phenomena  of 
the  fecretion  of  fat  (xix.)  agree  with  this  deferip- 
tlon.  Such  as  are  coagulable,  but  fpecificaily  heav- 


Chap.  VIL 


SECRETION. 


99 

rer  than  thofe  which  are  merely  watery,  and  which 
continue  fluid  in  the  living  animal,  pafs  from  the 
red  arteries,  into  others  which  are  pellucid,  but  con- 
tinuous to  the  red  ones,  and  fmaller  ; whether  thefe 
pellucid  ones  be  continued  on  as  trunks,  fending  off 
other  fmaller  branches,  fuch  as  the  arteries  of  the 
inferior  orders  (xli.)  or  whether  they  exhale 
their  contents  by  a fliort  extremity,  like  the  vefl’els 
of  CLXX. 

ccxxvi.  Thin  watery  fluids  may  evidently  pafs 
off  by  any  veflels  continuous  with  the  fanguiferous, 
or  inferior  orders  of  velfels  (xliv.)  provided  they 
be  only  fmail  enough  to  exclude  the  grofler  juices  : 
whether  thefe  proceed  from  the  fldes  of  the  larger 
veflels  ; or  whether  all  the  proper  fluids  being  fent 
Oif  through  the  larger  canals,  the  fmaller  canal  be 
continued  as  the  trunk,  as  in  the  eye.  To  the  pro- 
dudlion  of  thefe  fluids,  the  moft  Ample  fabric,  even 
the  direct  continuation  of  the  fecretory  artery  itfelf 
into  the  excretory  du£l,  is  fuflicient,  as  feems  prob- 
able in  the  urine.  Therefore,  in  this  cafe,  the 
ftru6ture  is  direct  and  Ample,  with  few  infle<3:ions, 
and  with  little  diminution  of  velocity. 

Such  juices  as,  being  watery^  are  lights  but  vif- 
cid  at  the  fame  time,  and  confequently  fluggifli 
and  tardy,  efcape  eafily  by  fliort  tubes  append- 
ed to  the  fanguiferous  arteries,  and  lefs  than  the 
adipofe  veflels  ; and,  therefore,  it  is  evident,  that 
thefe  will  be  feparated  from  the  blood  more  abun- 
dantly in  fome  parts  of  the  body,  where  the  veloc- 
ity derived  from  the  heart  is  lefs,  the  flexures  of 
the  artery  more  frequent,  and  the  length  of  the  ca- 
pillaries greater. 

cc XXVII.  Has  each  part  its  particular  ferments, 
form  of  pores,  fpeciAc  weight,  and  Alters  Ailed 
with  their  own  peculiar  humour,  and  refuAng  what- 
ever is  not  analagous  to  it,  which  determine  the 
nature  of  the  fluids  to  be  generated?  Let  thofe 
who  adopt  thefe  ideas,  conAder  the  great  varieties 
li  3 there 


foo 


SECRETION. 


Chap.  VIT. 


there  are  in  fluids,  feparated  in  the  fame  part  of  the 
body,  according  to  the  difference  of  age,  courfe  of 
life,  &c.  In  the  foetus,  the  bile  is  fweet  ; the  fe- 
men  thin,  and  without  animalcules  ; the  milk  wa- 
tery or  abfent ; the  urine  watery,  mucous,  and  in- 
fipid ; the  uterine  mucus  very  white  ; the  cuta- 
neous velfels  full  of  a red  fluid  ; the  aqueous  hu- 
mour red  ; and  the  fat  gelatinous.  In  the  fame  or- 
gans, in  an  adult  perfon,  the  bile  fecretcd  is  acrid  ; 
the  femen  thick  ; the  milk  but)Taceous  ; the  urine, 
yellow,  tiiin,  and  aikalefcent ; the  menftrual blood, 
and  the  aqueous  liumour,  very  limpid.  But,  even 
in  the  adult  perfon,  how  different  the  aqueous  urine, 
the  concocted  urine,  and  the  heavy  febrile  urine, 
replete  with  falts  and  oils  ? The  paflions  of  the 
mind,  v/hich  make  no  change  in  the  body  except  up- 
on thetenflon  of  the  nerves,  yet  wonderfully  change 
the  fecretions,  and  expel  even  the  blood  and  bile 
tlirough  the  velfels  of  the  flein.  Add  to  this,  the 
frequent  diflurbance  and  alteration  of  the  fecre- 
tions from  flight  caufes  ; fo  that,  different  augmen- 
tations of  velocity  fltall  caufe  different  liquors  to  be 
fecreted  by  the  fame  organ  : for  blood  has  been 
laiown  to  pafs  into  almoll  all  the  paffages  of  all  the 
fluids ; of  the  fweat,  tears,  mucus  of  the  noftrils, 
and  of  the  womb,  milk,  femen,  urine,  and  fat.  A 
true  milk  has  been  feen  feparated  by  glands  in 
the  thig;h.  VvTien  the  urine  is  not  excreted,  on  ac- 
count  of  fome  dcfecl  of  the  kidneys,  ureters,  or 
bladder,  it  has  been  exhaled  into  the  fkin,  ventricles 
of  the  brain,  or  into  the  whole  cellular  fabric.  The 
pcrfpirable  matter  of  Saneforius,  though  fo  fluid, 
by  cold  is  fent  off  by  the  urinary  paflages  ; and  by 
fear,  or  by  medicines,  through  the  excretory'  villi 
of  the  inteftines.  That  exhalin<x  A'ifcid  matter  of 
the  celluiar  fubftance  is  fecreted  and  abforbed,  and 
by  the  fame  organs,  alternately  with  the  fat,  fo  dif- 
ferent from  it  (xviii.)  Salivation  fupplies  the 
place  of  the  exhaling  fluid  of  Sanctorius,  the  cxhal- 


Chap. 


SECRETION. 


loi 


ing  fluid  fupplies  the  internal.  The  bile,  when 
abforbed,  evidently  pafles  into  the  vefl’els  of  the 
eyes.  It  appears,  that  there  is  not  any  thing  in  the 
particular  fabric  of  any  of  the  vifcera  or  glands, 
that  can  fo  fix  or  maintain  the  nature  of  the  fectet- 
ed  fluid  ; that  in  perfectly  entire  organs,  different 
fluids  may  not  be  feparated,  by  an  increafe  or  di- 
minution of  velocity,  or  alteration  of  the  ftricture 
of  the  nerves.  The  fpecific  gravities  of  the  vifcera 
and  ftrainers  do  not  correfpond,  even  according  to 
their  authors,  to  the  fpecific  gravity  of  the  huiuour^ 
which  they  fecrete  ; nor  are  they  at  all  known  by 
experiments  that  can  be  depended  on. 

ccxxviii.  It  now  remains  for  us  to  diicover,  how 
the  pure  fecretions  are  formed  in  a healthy  perfon. 
For  aU  the  fluids,  when  recently  fecreted,  without 
excepting  any,  not  even  the  oil,  are  mixed  v/ith  a 
great  deal  of  water  ; nor  does  it  feem  pofllble,  that 
any  of  the  thicker  juices  could  be  formed,  without 
having  a mixture  of  the  thinner  ones  : how  then 
do  the  femen,  bile,  oil,  and  mucus,  get  rid  of  their 
fiaperabundant  water,  and  acquire  their  proper  vif- 
cidity  and  other  qualities  ? 

ccxxix.  For  this  end,  nature  has  framed  glands 
and  follicles,  large  and  fmall,  for  thoie  fluids  from 
which  the  watery  paits  are  to  be  feparated,  in  or- 
der to  render  the  remaining  part  more  ftrong  and 
vifcid.  A flightly  mucous  water,  differing  at  firfi: 
very  little  from  the  perfpirable  vapour  or  from  tears, 
is  depofited  in  the  follicles  of  the  noftrils,  windpipe, 
and  inteftines.  This  is  not  continually  difcharging, 
becaufe  the  excretory  orifice  being  lefs  than  the 
follicle  (cxcvi.)  and  the  excretory  duct  being 
fometimes  long  and  flender,  at  others  repeatedly 
bent,  and  inffecied  or  tranfmitted  through  hard 
cellular  texture,  or  clofed  by  fome  force  equivalent 
to  a fphincter,  the  fluid  is  fo  retarded  that  it  can 
fcarcely  efcape  without  tlie  afliftance  of  extrinfic 
preflure  j unlefs  perhaps  the  follicle  being  irritated 


!02 


SECRETION. 


Chap.  VIT. 


by  its  quantity  or  acrimony,  prels  out  the  liquor 
incommoding  it,  by  a kind  of  periftalic  motion. 
I’his  appears  from  the  miorning  difeharges  of  mu- 
cus by  blowing  the  nofe,  coughing  up  from  the 
lungs,  and  by  fneezing  after  the  nocturnal  ftagna- 
tion.  In  the  mean  time,  the  patulent  veins,  ex- 
tended into  the  cavity  of  the  follicle,  abforb  the 
more  aqueous  parts  from  the  thin  mucus,  fo  that  it 
becomes  thicker  as  it  is  retained  longer  ; but  if,  by 
the  force  of  fome  ftimulus,  it  be  directly  difeharg- 
ed  after  it  is  fecreted,  it  comes  out  thin  and  wa- 
tery. Examples  of  this  we  have  in  the  urethra, 
in  the  noftrils,  and  in  the  earwax  ; as  alfo  in  the 
bile,  which,  at  its  firft  feparation  in  the  liver,  is 
■watery,  and  has  but  little  yeUownefs  or  bitternefs. 
It  is  therefore  detained  in  a bladder,  and  there 
digeiled  by  the  vital  heat ; its  thinner  parts  are 
abforbed  by  the  veins,  or  exude  through  the  mem- 
branes themfelves  ; whence  the  remainder  becom.es 
more  thick,  bitter,  and  oily.  The  fame  mechanifm 
takes  place  in  the  femen  ; which,  being  preferved 
in  the  feminal  velicle,  is  there  thickened,  fo  as  to 
be  very  vifeid  after  long  chaftity  ; while  after  re- 
peated venery  it  is  expelled  very  fluid.  In  fome 
places  nature  has  made  this  recepticle  double  or 
triple  in  the  fame  organ,  that  tlie  fluid  might  at- 
tain the  utmoft  degree  of  vifeidity.  In  the  femi- 
nal palTages,  the  rete  teftis  and  termination  of  the 
epididymis,  confrirute  a large  canal,  and  a large 
veiicle  ; while  the  vefleis  of  the  teflicle,  vas  deie- 
rens  and  proflate  dudl,  are  narrow.  Hence  there 
are  ncw'here  real  glands,  except  for  fecreting  a vif- 
eid liquor.  And  if  a vifeid  liquor  be  feparated 
from  arteries  without  a follicle,  it  always  ftagnates 
in  fome  conflderabie  follicle.  The  femen,  bile, 
liquor  of  the  joints,  and  fat,  afford  examiples  of 
this, 

ccxxx.  The  fluids  may  be  likewife  changed  in 
their  receptacles  by  the  afluflon  of  fome  new  li- 
quor. 


Chap.  VH. 


SECRETION. 


103 

qnor.  Thus  the  femen  is  thickened  by  the  addition 
of  the  liquor  of  the  proilate  ; the  chyle  is  attenua- 
ted by  mixture  with  the  faliva  of  the  pancreas  and 
the  gaftric  and  inteftinal  juices,  and  by  theaffuHon 
of  the  bile  it  becomes  alkaleicent ; the  albumen 
of  the  joints  is  tempered  by  the  tvco  kinds  of  fat 
(cxcv.) 

ccxxxi.  Laftly,  what  is  abforbed,  may  have  its 
ufes  in  the  animal  economy,  after  it  is  taken  into  the 
blood  ; thus  the  femen  gives  a furprifing  ftrength 
to  male  animals.  For  the  moft  part,  likewife,  in 
fluids  which  are  detained,  an  acrimony  of  an  al- 
kalefcent  nature  is  generated,  which  alfo  hath  its 
ufes,  as  in  the  bile  and  femen. 

ccxxxii.  But  the  moft  important  ufe  of  the 
follicles  and  receptacles  is  to  preferve  their  peculiar 
fluids,  for  thofe  times  in  which  alone  they  are  fubfer- 
vient  to  life,  and  that  a large  quantity  of  them  may 
be  collected  to  correfpond  with  their  ufes  at  certain 
periods.  Thus  the  bile  is  referved  for  the  time  of 
digeftion,  the  femen  for  due  venery,  and  the  mu- 
cus of  the  noftrils  is  accumulated  in  the  night  to 
moderate  the  force  of  the  air  palling  through  them 
in  the  day. 

ccxxxiii.  Therefore,  as  nature  has  framed  ma- 
chines which  retard  the  fluids  in  large  or  fmall 
follicles,  fo  flie  has  made  others  to  expel  them  at 
proper  times.  To  fome  glands  fhe  has  given  par- 
ticular mufcles  ; as  in  the  tefticles  of  brutes,  the 
urinary  bladder,  and  the  gaU  bladder,  and  in  the 
inteftines,  and  ftom.ach  *,  or  flie  has  fubjoined 
contiguous  mufcles  to  promote  the  difcharge,  as 
the  biventer,  malfeter,  mufcles  of  the  abdomen 
and  diaphragm  ; or  elfe  Ihe  has  given  them  a kind 
of  nervous  irritability,  which,  being  excited  to 
aftion  by  an  indefcribable  ftimulus,  opens  the  Ihut 
paflages  to  the  milk,  femen,  tears,  &c.  or  from 
the  contact  of  any  thing  acrid,  as  already  mention- 
ed, accelerates  the  difcharge  of  the  fluid  ■,  as  hap- 
pens 


RESPIRATION. 


104 


Chap.  MH. 


pens  to  the  bile,  liquor  of  the  ftomach  and  intef- 
tineSj  and  to  the  febaceous  matter. 


CHAP.  vni. 


RESPIRATION. 


ccxxxiv.  p ’TIE  bags  of  the  pleura  (lxxvii. 

Lxxviii.)  are  fiUed  by  the  lungs  ; by 
which  we  underhand  two  vifcera,  one  right  and 
another  left,  in  figure  correfponding  with  the  bags 
themfelves  which  they  fill,  having  a broad  balls 
below,  and  being  terminated  above  at  the  firft  rib 
by  an  obtufe  cone.  Anteriorly  their  furface  is  flat, 
laterally  convex,  and  pofterioiiy  it  is  rounded  ; in- 
ternally it  is  concave,  efpecialiy  that  of  the  left 
lungs,  for  the  purpofe  of  containing  the  heart. 
The  right  lung  is  the  largeft,  and  is  moft  frequent- 
ly divided  into  three  lobes  ; which  is  feldom  the 
cafe  with  the  left.  They  are  freely  fufpended  by 
the  great  blood-vcffels  ; unlefs  you  call  that  a liga- 
ment which  is  formed  at  the  bafis  of  the  dia- 
phragm by  the  external  membrane  of  the  pleura 
going  off  to  the  lungs.  Between  the  lungs  and 
pleura  is  found  a watery  vapour,  of  a coagulable 
nature,  like  that  of  the  pericardium  (lxxxii.) 
which  tranfudes  from  the  lurface  of  the  lungs  and 
of  the  pleura,  continually  in  the  foetus,  and  not  un- 
frequentlp  in  the  adult.  In  dropfy,  this  vapour 
is  increafed,  or  thickens  to  a kind  of  febaceous 
matter  ; or,  iaftly,  it  concretes  into  fibres,  forming 
adiiefions  of  the  lungs. 

ccxxxv.  The  external  membrane  of  the  lungs 
is  fimple,  and  thinner  than  the  pleura,  although 
continuous  with  it.  It  fprcads,  from  the  adiiellon 
of  the  great  blood-vefiels  of  the  heart,  over  the 
lungs  in  every  direction,  and,  when  entire,  may 
be  eafily  inilated,  even  after  being  feparated  from 


Chap.  Vm. 


RESPIRATION. 


105 

the  lungs.  The  fame  membrane  paffes  over  the 
intervals  between  the  lobules,  like  a bridge.  It  is 
joined  to  the  lungs  by  cellular  texture. 

ccxxxvi.  The  lungs  are  made  up  of  lobes  fepa- 
rated  by  intermediate  intervals,  in  which  there  is 
loofe  cellular  fubftance.  Their  firft  divifion  is  in- 
to two  large  lobes,  and  one  middle  one  of  a fmall- 
er  fize  ; which,  however,  cohere  together  : they 
are  afterv/ards  repeatedly  fubdivided  into  fuccef- 
fively  fmaller  lobes,  always  furrounded  by  cellular 
membrane,  till  at  lad  the  lobules  are  refolved  into 
very  fmall  membranous  cells,  which,  in  adults,  are 
filled  with  air,  are  of  various  figures,  and  com- 
municate on  aU  fides  with  each  other.  The  ele- 
mentary parts  of  the  lungs,  therefore,  are  not  oval 
bags,  furrounded  by  mufcular  texture,  with  a fin- 
gle  orifice  which  receive  the  air  from  the  windpipe, 
but  they  admit  the  air  exhaling  from  the  ultimate 
branches  of  the  trachea,  fo  that  being  effufed  into 
irregular  fpaces,  it  paffes  and  repaffes  freely  from 
any  one  portion  of  the  lungs  into  all  the  others. 
This  is  demonftrated  by  inflation,  for  air  blown 
into  any,  even  the  moft  minute  lobule,  through  its 
branch  of  the  trachea,  paffes  into  all  the  reft.  In 
man  and  in  the  fmaller  animals,  the  cellular  fabric 
of  the  intervals  is  neither  fhut  up  from  the  veficies 
of  the  lungs,  nor  are  the  lobes  furrounded  by- any 
peculiar  membrane  •,  in  the  largeft  animals,  there 
is  no  communication  between  the  air  veficies  and 
the  cellular  fpaces  which  furround  the  lobules. 

ccxxxvii.  The  air  paffes  into  thefe  veficies 
through  the  windpipe.  The  windpipe  arifes  from 
the  larynx  (hereafter  to  be  defcribed,)  and  receives 
the  air  through  it  alone.  Its  firft  part  fingle  and 
fimple,  partly  flefliy  and  partly  cartilaginous,  the 
cefophagus  lying  below  it  and  to  its  left,  is  fup- 
ported  on  the  broad  and  flat  vertebrs  of  the  neck ; 
in  other  vcords,  within  the  cellular  fubftance  that 

furrounds 


Iq6 


RESPIRATION. 


Chap.  VTIT. 


farrounds  the  v.dndpipe,  there  is  fituated  a canal, 
compofed  of  alternate  cartilaginous  and  mufcular 
rings.  The  cartilaginous  rings,  thin  and  elaftic, 
anteriorly  fomewhat  fiat  and  thick,  are  joined  to- 
gether by  their  pofterior  extremities,  which  are 
thinner  ; and  the  cirple  is  completed  by  ftrong  tranf- 
verfe  mufcular  fibres,  adhering  to  both  the  loofe 
extremities  of  the  cartilage.  The  lower  circles  arc 
lefs ; the  uppermoft  is  often  augm.ented  by  an  ap- 
pendix,  that  next  to  the  divifion  is  perpendicular. 

ccxxxviii.  The  flefhy  rings,  fituated  alternately 
with  the  cartilaginous  ones,  are  compofed  of  red 
mufcular  fibres.  Some  of  thefe  are  tranfverfe,  con- 
nefting  the  detached  ends  of  the  annular  cartil- 
ages 5 others  defeend  from  each  upper  to  the  next 
lower  ring.  But  other  mufcular  fibres  again,  de- 
feend  from  the  cricoid  cartilage,  and  having  reach- 
ed" below  the  divifion  of  the  bronchia,  vanifh  upon 
the  lungs.  The  tranfv'erfe  fibres  contract  the 
windpipe  ; the  longitudinal  ones  fhorten  it. 
Within  the  lungs,  between  the  imperfect  rings, 
there  is  a fort  of  mufcular  fabric,  but  lefs  uniform- 
ly difpofed. 

ccxxxix.  In  the  cellular  coat  which  furrounds  the 
mufcular  one,  but  efpecially  behind,  in  the  inter- 
val between  the  cartilages  (ccxxxvi.)  are  placed 
numberlefs  fimple  glands,  which,  by  very  fnvall 
ducts,  like  pores,  opening  into  the  ca\dty  of  the 
windpipe,  depofitc  within  that  cavity  a watery 
and  pellucid  mucus,  not  coagulable  into  films,  and 
xery  bland,  which  is  of  the  greatefl  ufe  in  defend- 
ing the  exceedingly  fenfible  membrane  from  the 
impurities  of  the  air,  which  is  loaded  with  particles, 
irritating  by  their  mechanical  figure  or  chemical 
acrimony.  Numerous  conglobate  glands  are  fitua- 
ted around  the  trachea  and  its  bronchia,  but  thefe 
are  of  the  lymphatic  kind,  although  their  black 
fluid  frequently  penetrates  into  the  trachea,  l.aft- 


Chap.  VIII. 


RESPIRATION. 


loy 

ly,  the  internal  tube  of  the  windpipe  is  lined  by  a 
membrane,  covered  by  epidermis,  continuous  with 
the  fidn  and  miembranes  of  the  mouth,  fmooth, 
foft,  and  very  irritable.  It  is  connected  with  the 
mufcular  coat  by  cellular  fubftance. 

ccxL.  The  veffels  of  this  entire  part  of  the 
windpipe,  in  the  neck,  come  from  the  lower  thy- 
roids ; in  the  thorax,  from  other  fmall  branches 
of  the  fubclavian  trunks,  or  the  mammaries,  or  the 
bronchials  properly  fo  called.  Its  nerves,  ariling 
from  the  recurrent  and  intercoftals,  are  numer- 
ous. 

CCXL  I.  In  the  upper  part  of  the  thorax,  the 
windpipe  is  received  between  the  laminse  of  the 
pofterior  mediaftinum  ; and  at  the  third  vertebra, 
or  a little  above,  is  divided  into  two  branches  limi- 
lar  to  the  trunk,  formed  in  like  manner  of  imper- 
fect cartilages,  and  furniflied  with  limilar  glands  ; 
each  of  thefe  enters  the  lung  to  which  it  corre- 
fponds,  and  the  right  is  fomething  Ihorter  and  larg- 
er than  the  left.  Having  entered  the  lungs,  the 
cartilaginous  rings  gradually  degenerate  into  frag- 
ments, become  more  difform,  gnomonic,  angular, 
triangular,  and  intermixed  with  a larger  portion  of 
membrane,  till  at  length,  by  the  diminution  of  the 
cartilages,  the  ultim.ate  branches  of  the  bronchia 
become  membranous. 

ccxLii.  Its  ultimate  branches  are  invilible,  and 
exhale  air  into  the  cellular  fpaces  of  the  lungs  in 
adults,  and  from  the  fame  fpaces  receive  the  arterial 
expired  vapour. 

ccxLiii.  The  veffels  of  the  bronchia,  are  the 
bronchial  veins  and  arteries.  The  latter  are  gen- 
erally two  ; one  coming  from  the  upper  intercof- 
tal  of  the  aorta,  which  is  diftributed  either  to  the 
right  only,  or  to  both  the  lungs  ; the  other,  from 
the  trunk  of  the  aorta,  goes  to  the  left  lung.  Some- 
times there  are  m.ore  ; as  when  there  are  three,  by 
the  addition  of  a fecond  from  the  aorta.  At  other 

tiinesj 


RESPIRATION. 


Chap.  VIH. 


loS- 

times,  there  is  only  one  artery  common  to  both 
lungs.  The  thoracic  part  of  the  bronchia,  fituated 
without  the  lungs,  has  its  proper  veffels  from  the 
ao.rta,  or  from  the  fubclavian,  or  the  mammary, 
or  the  intercoftal.  The  bronchial  veins  are  very 
commonly  two  ; the  right  from  the  vena  azygos, 
the  left  from  a peculiar  branch  of  the  fubclavian 
vein,  the  left  faperior  intercoftal.  Thefe  blood- 
veffels  accompany  the  branches  of  the  trachea ; and 
defcend  into  their  membranes,  the  arteries  inofcu- 
late  with  the  pulmonary  arteries,  and  the  veins  with 
the  veins,  forming  a vafcular  web  in  the  internal 
cellular  fubftance.  There  are  forne  inftances  where 
the  pulmonary  vein  itfelf  has  given  fmall  branches 
to  the  lungs,  to  the  windpipe,  and  to  the  furface 
of  the  lungs. 

ccxLTv.  But  there  are  other  largrer  veffels  belone:- 
ing  to  the  lungs,  the  pulmonary  artery  (cvi.  cviii.) 
and  the  vein  (cx.)  The  great  artery,  in  the  foetus 
larger  than  the  aorta,  and  in  the  adult  but  little 
lefs,  has  two  branches  ; the  right  lai'ger  but  Ihorter, 
the  left  narrower  and  longer.  In  the  foetus,  the 
trunk  itfelf  is  continued  into  the  defeending  aorta, 
and  is  known  by  the  name  of  duclus  arteriofas.  In 
the  adult,  that  trunk  degenerates  into  a folid  liga- 
ment. The  four  pulmonary  veins  accompany  the 
branches  of  the  artery  and  of  the  trachea,  through 
the  lungs,  fiarrounded  by  a good  deal  of  cellular  fub- 
ftance ; which  fubftance,  being  increafed,  at  laft 
compofes  the  lungs  themfelves.  Witlftn  this  cellular 
fabric,  the  air-veff'els  and  blood-veffels  are  fubdivid- 
tsd,  and  in  the  ultimate  cellular  fpaces,  the  ultimate 
veins  and  arteries  fpread,  reticularly  interwoven  ; 
and  here  the  fmall  arteries  exhale  a plentiful  vapour 
into  the  aerial  cells  of  the  lungs,  and  the  veins  ab- 
forb  a watery  vapour  from  them.  Hence  coloured 
v/ater,  the  whey  of  milk,  or  thin  wax,  being  inieef- 
cd  into  the  pulmonary  artery,  flow'  with  troth  into 
the  windpipe  5 or,  on  the  contrary,  penetrate  from 


Chap.  VIH. 


RESPIRATION. 


tog 

the  bronchia  into  the  ptilmonary  artery.  In  like 
manner,  injedions  pafs  from  the  pulmonary  vein 
into  the  bronchia  ; or  from  thence,  into  the  veins- 
Laftly,  they  readily  pafs  from  the  arteries  into  the 
pulmonary  veins  j or  return  from  the  veins  into  the 
arteries. 

ccxLv.  The  lymphatic  veffels,  as  in  other  parts, 
form  a network  upon  the  furface  of  the  lungs, 
from  whence  branches  run  to  the  cavity  of  the 
pofterior  mediallinUm,  to  the  glands  feated  on  the 
cefophagus,  and  to  the  thoracic  dud.  The  nerves 
are  fmaJl,  efpecially  the  anterior,  the  pofterior  ones 
being  fomewhat  larger : they  come  from  a nerve 
of  the  eiglrth  pair  ; but  they  receive  fome  addition, 
accompanying  the  large  blood- vefiels,  from  the  re- 
current, and  likewife  from  the  cardiac  plexus. 
Hence  the  lungs  have  but  little  fenfation ; but  that 
of  the  little  nerves,  divided  upon  the  fubftance  of 
the  bronchia,  is  very  acute.  Nor  are  the  lungs  of 
an  irritable  nature. 

ccxLvi.  The  quantity  of  blood  which  enters  into 
the  lungs  is  exceedingly  great,  equal  to  (or  even 
perhaps  greater  than)  that  which  is  fent  in  the  fame 
time  throughout  the  reft  of  the  body ; which,  there- 
fore, indicates  this  vifcus  to  be  fubfervient  to  fome 
very  important  purpofe.  That  this  ufe  depends 
manifeftly  upon  the  air,  appears  from  the  univerial 
confent  of  nature,  in  which  we  fcarcely  find  an  ani- 
mal which  does  not  refpire  ; alfo  from  the  ftrudure 
of  the  lungs  in  the  foetus,  in  which  being  ufelefs, 
on  account  of  the  abfence  of  air,  they  receive  only 
a very  fmall  portion  of  that  blood,  which  the  pul- 
monary artery  conveys  from  the  heart.  We  come. 
Therefore,  to  ipeak  of  refpiration,  or  the  inhalation 
and  expulfion  of  air  by  the  lungs. 

ccxLvii.  Air,  phyfically  confidered,  is  an  ele- 
ment, fluid,  invifible,  elaftic,  with  an  indeftrudible 
fpring,  and  foniferous.  But  the  air,  which  we  com- 
monly receive  into  the  lungs,  is  impure,  fiUed  with 
a great  quantity  of  watery  and  other  vapours,  alfo 

with 


tio 


RESPIRAllOI'T. 


Chap.  \TII. 


wth  falls,  and  the  univerfal  acid,  with  the  feeds*  of 
|jlants  and  animals,  and  other  foreign  particles  ; and 
is  ponderous  *,  weighing,  however,  8 50  times  lefs 
than  water,  a cubic  foot  of  air  being  between  610 
and  694  grains.  This  air,  which  furrounds  the  earth 
on  all  lides,  being  compreiTed  by  its  incumbent  col- 
umns, perpendicularly  and  laterally,  enters  with 
great  force  wherever  it  meets  with  lefs  reirftance, 
as  appears  from  experiments  made  in  vacuo,  and 
from  the  phenomena  of  the  air-pump  ; fo  that  its 
preillire  on  the  human  body  is  not  lefs  than  30,000 
pounds.  It  is  repelled  chiehy  by  the  pores  of  mem- 
branes, though  thefe  are  permeable  by  water ; it 
likewife  penetrates  oil  or  mucus  with  difficulty. 

ccxjLviii.  The  ambient  air  is  excluded  from  all 
parts  of  the  human  body,  by  denfe  Ikin,  which, 
even  when  dry,  is  impervious  to  the  air  ; by  the  fat 
lying  under  it ; by  the  narrownefs  of  the  abforbent 
yeffels,  and  by  the  equability  of  the  refiftance.  We 
muft  inveftigate  why  the  air  enters  the  lungs,  which 
in  an  adult  are  always  filled  with  air,  and  therefore 
refill  the  prefiure  of  the  whole  atmofphere  with  an 
equivalent  force.  That' the  lungs  always  contain  air, 
is  e\ddent ; becaufe,  however  you  comprefs  them, 
they  are  ftill  lighter  than  w*ater  ; and  even  after 
they  have  been  inflated  but  a few  times,  they  always 
fwim  ; whereas,  in  the  foetus,  before  air  has  been 
admitted  into  them,  they  fink  to  the  bottom. 

ccxLix.  On  the  equilibrium  being  deftroyed,  the 
air  invariably  defeends  in  ev^ery  direction  to  that  place 
where  it  meets  with  kail  refiftance  (ccxnvii.)  But 
air  that  is  denfe  and  heaay  defeends  more  eafily 
than  that  which  is  light,  whofe  force  fcarcely  ex- 
ceeds that  of  the  air  in  the  lungs,  nor  is  able  by  the 
fame  force  to  overcome  the  refillance  of  the  bron- 
chia, and  of  the  force  by  which  the  air  contained 
in  the  lungs  is  compreiTed.  Hence  an  animal  lives 
with  greater  eafe  in  a denfe  than  in  a light  atmof- 
phere : although  that  air  is  alwavs  better  tolerated. 

wluch 


Chap.  VIII. 


RESPIRATION. 


iij 


which  is  pure  in  proportion  to  its  levity  ; fuch  as 
that  of  the  higheft  mountains  of  the  Alps.  There- 
fore, that  the  air  may  enter  the  lungs,  they  muR 
make  a lefs  refiftance  to  it  than  before  ; namely, 
the  air,  wfiich  is  already  in  the  cellular  fabric  of 
the  lungs,  muft  be  rarefied : but  this  effeft  will  be 
produced,  if  the  cavity  of  the  breaft,  which  is  filled 
by  the  lungs,  be  dilated.  The  air,  which  is  always 
in  the  lungs,  expands  into  this  increafed  fpace,  by 
which,  being  weakened  in  its  fpring,  it  makes  lefs 
refinance  to  the  external  air  ; confequently  a por- 
tion of  external  air  defcends  into  the  lungs,  fuffi- 
cient  to  reftore  to  the  air,  now  contained  in  the 
lungs,  the  fame  denfity  with  that  of  the  external 
air. 

ccL.  We  muft,  therefore,  defcribe  the  powers 
\yhich  dilate  the  breaft.  The  breaft  or  thorax  is 
compofed  of  bones,  mufcles,  and  cartilages  ^ being 
almoft  of  the  Ihape  of  an  elliptic  barrel,  fomewhat 
comprefled  before,  but  behind  divided  by  an  emi- 
nence, whofe  hoops  are  the  ribs,  and  of  remarkable 
ftrength.  In  the  lateral  parts  of  this  ftruclure,  tlie 
lungs  are  fituated  ; the  central  and  lower  parts  con- 
tain firft  the  pericardium,  and  then  fome  of  the 
abdominal  vifcera. 

ccLi.  The  bafis  of  the  thorax  is  formed  by  a 
column,  a little  curved,  at  the  upper  part  gibbous 
backwards,  fo  that  its  fummit  is  fituated  moft  be- 
hind. To  this  twelve  vertebrae  are  affixed.  But 
they  alfo  coalefce,  by  the  union  of  their  bodies  into 
a fingle  column,  which  projefts  forwards  between 
the  two  cavities  of  the  breaft ; divides  the  right 
from  the  left  ; and  is  plain  in  the  forepart,  and 
broad  towards  the  fides.  A flight  finuofity  receives 
the  ribs  into  that  place  where  the  arch  feparates 
from  the  body.  They  are  bound  together  into  one 
column,  both  by  the  elaftic  plate  interpofed  be- 
tween the  bodies  of  every  two,  and  coalefcing  with 
both ; and  by  other  ligaments  and  fpines  lying  up- 


RLSPIRATIOI^. 


Chap.  YUl, 


it2 

on  one  another,  and  by  the  junclion  of  the  ribs ; 
on  which  accounts  they  fcarcely  admit  of  motion 
amongft  themfelves.  The  fides  of  the  brcaft  are 
formed  of  twelve  ribs.  Thefe  are  in  general  bent 
in  the  form  of  an  irregular  arch,  having  a conlider- 
abie  curvature  laterally  and  backwards,  but  extend- 
ing in  their  forepart  towards  a right  line.  I'he 
bony  parts  of  the  ribs  are,  however,  parallel  with 
each  other.  The  greateft  part  of  the  rib  is  bony  ; 
of  which  the  pofterior  portion  is  round  and  thick, 
and  the  anterior  thin  and  flat.  The  anterior  remain- 
ing part  of  the  rib  confifls  of  a cartilage  ; which  in 
general  preferves  the  ligure  of  the  rib,  broad,  flat, 
adhering  to  an  irregular  hoUow  of  the  bony  part  ; 
and  which  does  not  change  into  bone,  unlcfs  in  ex- 
treme old  zg;e. 

ccLii.  The  poflerior,  bony,  and  thick  part  of 
each  rib  terminates  in  a head.  Thefe  are  inferted 
into  pits  fcooped  out  of  the  bodies  of  the  upper- 
moft  and  two  iowermoft  vertebrae,  and  in  the  con- 
tiguous margins  of  each  of  the  other  two.  The 
vertebrae  are  tied  to  the  ribs  by  flrong  ligaments,  of 
which  the  principal  is  diftributed  upon  each  adja- 
cent vertebra,  in  a radiated  manner  from  each  rib  ; 
other  ligaments  tic  the  tranfverfe  procefs  to  the  tu- 
bercle of  the  rib,  and  others  connect  the  contiguous 
ribs,  and  alfo  the  tranfverfe  procefles,  with  each 
other.  Moreover,  between  the  angle  of  incurva- 
llon  and  the  articulation  with  the  vertebrae,  each  of 
the  ten  upper  ribs  has  a tubercle,  wliich,  being  con- 
nefted  with  the  plain  fide  of  the  tranfverfe  procefs 
of  the  correfponding  vertebra,  are  tied  by  fiiort  and 
flrong  ligaments  to  that  procefs,  in  fuch  a manner, 
that,  w'hilc  the  juncture  is  very  flrong,  the  rib  can 
afeend  and  defeend  for  a fliort  way. 

ccLiii.  Of  the  anterior  cartilages,  the  feven  upper- 
iTiofl;  reach  to  the  fternum,andfl;rengthcncd  hy  Ihort 
ligaments,  they  enter  with  a double  head  into  lateral 
dcpvcflions  in  that  bone,  which  are  incrufled  with 

cartilage. 


Chap.  VIII. 


respiration. 


1^3 


cartilasce.  Of  the  five  remainins:  ribs,  the  ucner- 
moft  is  agglutinated  by  Rrong  cellular  fubftance  to 
the  ieveii!:h,  and  each  lower  one  to  the  one  imme- 
diately above  it,  fo  t-hat  they  form  a continuous 
margin,  which  is  itfelf  faiiered  to  the  fternurn. 
The  cartilages  are  connected  with  each  otheiv  both 
by  proper  ligaments,  and  by  cartilaginous  appen- 
dages joined  by  cellular  fubftance:  the  two  low-er- 
moft  are  free,  and  connected  only  with  the  muf- 
cles.  Thefe  inferior  cartilages  are  united  to  one 
another  and  to  the  fternum  by  ftrong  ligaments. 
ccLiv.  The  firft  rib  is  the  ftiorteft  and  moft  Iblid. 


As  they  follow  in  ftacceilion  to  the  feventh  and 
eighth,  every  two  of  them  form  larger  and  more 
moveable  circles.  The  eighth  is  the  longeft  of  all ; 
and  below  it,  they  always  become  Ihorter,  the 
lower  they  are. 

ccLv.  The  upper  rib  defcends ; the  fecond  joins 
the  fternum  alrnoft  at  a right  angle,  while  the 
others  afcend  both  to  the  vertebrae  and  to  the  fter- 
tium,  but  more  to  the  latter.  The  bony  part  or 
the  ribs  is  placed  in  fiach  a direftionj  that  the  up- 
permoft  have  their  anterior  furface  declined  for- 
wards, alrnoft  tranfverfely.  About  the  third  rib 
it  is  placed  alrnoft  perpendicularly  ; and  below'  the 
middle  ones,  it  prcjecls  a little  forwards.  Eefides, 
the  ftrength  of  the  ribs  is  very  different.  The'up^ 
permoft,  being  lliort,  tranfverfe,  rather  united  than 
articulated  with  the  fternum,  and,  laftly,  often  con- 
folidated,  make  the  greateft  reftftance.  Tlie  mo-* 
bility  of  the  lower  ribs  increafes  fucceffively  to  the 
loweft,  which,  adhering  only  to  mufdes,  moves 
moft  freely  of  ail. 

ccLvi.  The  fternum  in  general  is  a thin  fpongy 
bone,  in  adults  of  a fmgle  piece,  but  in  the  f-retus 
varioufly  multiplicate.  Its  upper  part  is  broader, 
oefagonai,  and  ftipported  by  the  cla’N  ides,  vchich 
are  united  with  it  by  a triangular  head,  and  very 
ftrong  articulation,  and  by  the  firft  rib  cn  each  fide. 


I 


RESPIRATION. 


Chap.  VUE 


II 4 

The  next  part  which  is  longer  and  narrower,  grows 
broader  downwards,  and  its  lides  receive  the  ribs 
into  proper  angular  cavities.  The  lower  part, 
which  is  iefs  and  Ihorter,  is  obtufely  fliaped  like  a 
tongue.  This  is  continued  into  a detached  appen- 
dage, partly  bony,  and  partly  cartilaginous,  which 
is  called  the  enliform  cartilage  ; of  various  Ihapes, 
being  foinetimes  obtufe  like  a little  tongue,  fonie- 
times  pointed,  fometimes  bifid,  and  foinetimes  per- 
forated. 

ccLvii.  In  order,  therefore,  to  dilate  the  feat  of 
the  lungs,  and  thus  to  produce  that  condition  which 
caufes  the  external  air  to  defcend  into  the  lunjis, 
the  thorax  muft  be  elevated.  For  thus  all  the  fec- 
tions  of  the  thorax  form  right  angles,  and  its  ca- 
pacity is  increafed.  This  motion  is  performed  by 
various  mufcles,  v.'hich  either  operate  conftantly, 
or  only  at  certain  times.  The  whole  of  the  in- 
tercofial  mufcles,  always  elevate  the  ribs.  Under 
this  name  we  comprehend  22  mufcles;  of  which 
1 1 are  external  or  I'ubcutaneous  ; and  as  many  in- 
ternal, leparated  from  the  pleura  only  by  fat  and 
cellular  fubfiance.  The  origin  of  the  external  in- 
tercoilals  is  at  the  pofterior  articulation  of  the  ribs 
(ccLii.)  their  anterior  termination  is  in  the  bony 
part  of  each  rib,  at  fame  diftance  from  the  carti- 
lage, fo  that  the  remaining  fpace  between  the  car- 
tilages, all  the  way  to  the  fternum,  in  place  of  the 
mufcles,  is  filled  with  an  aponeurofis.  Their  di- 
recfion  is  fuch,  that  they  defcend  obliquely  for- 
v/ards,  from  the  lower  edge  of  the  upper  rib  to  the 
upper  edge  of  the  lower  rib.  Almoft  all  authors 
agree,  that  they  elevate  the  ribs  ; becaufc  they  de- 
fcend from  the  upper  and  more  fixed,  to  the  lower 
and  more  moveable  rib,  in  fuch  a manner,  that 
their  lower  point  lies  more  diftant  from  the  verte- 
bral articulation,  or  fulcrum  of  the  lever  of  the 
ribs. 


ccnviii. 


RESPIRATION. 


Chap.  VIIl. 


ccLviii.  But  the  internal  intercoftals  arife  at 
fome  diftance  from  the  vertebrse,  near  the  on  tilde 
of  the  tubercles  (cclii.)  From  thence  they  pro- 
ceed as  far  as  the  fternum.,  into  which  the  firfc  of 
this  kind  are  inierted  above.  Except  the  anterior 
part  of  the  firft  internal  mufcles,  their  direction  is 
contrary  to  that  of  the  former  ; fo  that  they  de- 
fcend  backwards,  from  the  lower  margin  of  the  up- 
per rib,  to  the  upper  edge  of  the  lower  rib.  There- 
fore their  action  is  difputed,  becrmfe  their  lower 
infertion  is  made  into  a point  of  the  rib,  nearer  its 
articulation  with  the  vertebras,  which,  therefore, 
feems  to  be  the  leaft  moveable  : however,  they  el- 
evate the  ribs  notwithftanding  this  ; for  the  immo-* 
bility  of  the  upper  rib,  arihng  from  its  articulation, 
weight,  and  ligaments,  far  exceeds  the  mobility 
produced  by  its  greater  diftance  from  the  fulcrum. 
This  is  proved  by  the  difledtion  of  living  animals  ; 
in  which  it  appears,  that  the  internal  mufcles  act 
during  the  elevation  of  the  ribs,  and  reft  when 
they  are  dcprefled ; by  threads  fixed  to  a flexible 
human  Ikelcton,  and  drawn  in  the  direction  of  the 
internal  intercoftal  mufcles,  which  always  and  in- 
variably raife  the  inferior  rib  towards  the  fuperior ; 
and  by  the  firmnefs  of  the  upper  ribs,  which  ferve 
as  a fixed  point  to  the  lower  ones  : for  the  firft  ribs 
are  from  eight  to  twelve  times  lefs  moveable  than 
the  other  true  ribs  ; while  the  difference  of  diftance 
from  the  centre  of  motion,  is  fcarcely  the  twentieth 
part  of  the  whole  lever.  And  laftly,  by  experi- 
ment on  the  dead  fubjeft ; for,  on  raifing  its  tho- 
rax, the  internal  intercoftals  fwell. 

ccLix.  By  the  action,  therefore,  of  thefe  mufcles, 
the  thorax  is  elevated,  not  altogether  as  one  ma- 
chine, nor  would  refpiration  be  aflifted  by  fuch  a 
motion  ; but  the  ribs,  turning  upon  their  articu- 
lations, behind  are  but  little  moved,  while  with 
their  anterior  extremities,  they  defcend  and  form 
larger  angles  both  with  the  fternum  and  vertebne  ; 

J 2 .and 


ti6 


RESPIRATION. 


Chap.  Vllt 


and  in  the  middle  of  their  arches,  they  afcend  and 
raife  their  lower  edges  forv.^ards.  At  the  fame 
time,  the  Rernum  is  thruft  forward  from  the  verte- 
bras and  from  fhe  junctures  with  the  ribs.  Thus 
the  ribs  are  both  farther  from  the  vertebrx,  and 
the  right  ribs  recede  from  the  left ; and  both  diam-. 
eters,  from  the  right  to  the  left,  and  from  the 
fternum  to  the  vertebrx,  are  increafed  by  almoR 
two  lines  each  ; and  as  this  occurs  in  every  imagin- 
able fection  of  the  thorax,  the  cavity  of  the  breall 
will  be  fufficiently  dilated.  This  happens  efpecial- 
ly  in  women,  and  in  men  whofe  breathing  is  fome- 
what  laborious.  Thefe  effects  are  produced  leafl 
of  all  by  the  nrft  ribs,  but  more  by  the  fucceeding 
ones.  In  ftrong  infpirations,  the  ribs  defeendboth 
behind  and  before,  and,  along  with  thefe,  the  fter- 
num ; and  the  fpaces  between  the  cartilages  are 
leffened.  But  this  dilatation  is  neither  futlicient 
for  healthy  refpiration,  nor  is  it  almofl  obfeiA^abie 
in  men  ; although  even  tlien,  the  intercoftal  mufcleSy 
by  retaining  and  elevating  the  ribs,  very  much  aflifl 
the  infpiration  in  a fccondary  way,  by  affording  a 
fixed  point  to  the  diaphragm,  fo  that  the  whole 
force  of  that  rnufcle  may  be  fpent,  not  in  deprefllng 
the  ribs,  but  in  lov.^ering  itfelf.  The  greater  part, 
therefore,  of  the  fpace  which  the  thorax  gains  in 
infpiration,  arifes  from  the  action  of  the  diaphragm. 

ccLX.  By  the  diaphragm  we  underhand  a 
mufeie  expanded  in  a curvilineal  plate,  which,  in 
general,  feparates  the  pulmonary  bags  from  the 
abdomen  in  fuch  a manner,  that  the  middle  and 
tendinous  part  is  the  higheft,  and  fupports  the  peri- 
cardium ; that  the  lateral  portions,  which  arife  from 
the  folid  parts  of  the  thorax  and  loins,  are  every 
W'here  lower  j and  that  its  pofterior  portions  are 
lovreft  of  all.  The  flefhy  fibres  of  this  rnufcle  arife 
from  the  internal  or  pofterior  furface  of  the  cnli- 
form  cartilage  to  the  very  point,  and  from  the 
fixth,  feventh,  eighth,  ninth,  tenth,  eleventh  ribs. 


Chap.  Vni. 


RESPIRATION. 


117 

and  apex  of  the  twelfth  ; after  which  follows  an 
interval,  in  which  the  naked  pleura  is  contiguous 
to  the  peritonaeum.  Thereafter  mufcular  appen- 
dages of  the  diaphragm,  much  ftronger,  collected 
into  two,  three,  or  four  round  mufcles  on  each 
lide,  arife  flefliy  from  the  tranft^erfe  procefs  of  the 
fiift  lumbal  vertebra,  and  from  the  lide  of  the  body 
of  the  fecOnd  ; and  tendinous  from  the  middle 
of  the  body  of  the  fecond,  third,  and  fourth,  and 
from  the  cartilages  placed  between  them,  on  the 
whole  higher  up  in  the  left  fide,  and  lower  down 
in  the  right. 

ccLxi.  All  thefe  fibres  (cclx.)  becoming  ten- 
dinous, form  the  centre  of  the  diaphragm,  which 
refembles,  in  figure,  an  obtufe  gnomon,  and  fupports 
the  pericardium  .with  its  middle  and  broader  angle, 
while  the  lateral  wings,  of  which  the  left  is  nar- 
rower, defcend  backv^^ards.  This  central  portion  is 
more  moveable  than  the  reft ; but  in  the  middle 
tendinous  part,  and  neighbouring  mufcular  fub- 
ftance,  it  is  refifted  by  the  heart ; the  lateral  wings 
and  contiguous  portions  are  the  mmft  moveable. 
The  fibres  of  this  tendon  form  a moft  beautiful 
w'eb,  principally  indeed  on  the  upper  part ; which 
ftretches  from  each  mufcular  portion,  to  the  muf- 
cular portion  oppofite  to  it : and  then  they  form  re- 
markable inferior  fafciculi,  tranfverfe,  right,  left, 
and  pofterior,  which  laft  portion  is  the  uppermoft. 

ccLxii.  There  are  two  holes  in  the  diaphragm  ; 
of  which  the  right,  in  the  right  fide  of  its  tendon, 
is  obtufely  fquare,  and  circumfcribed  by  four 
ftrong  tendinous  fafciculi ; the  left,  which  is  ellip- 
tical, lies  betwixt  the  right  and  left  fleftiy  portions, 
arifing  from  the  middle  of  the  bodies  of  the  lumbal 
vertebrae  : under  this  opening  they  deculfate  and 
crofs  each  other  once  and  again,  but  above  they 
end  in  the  tendon.  Therefore  it  is  probable  that 
the  latter  is  contrafted  during;  the  action  of  the 
diaphragm,  and  that  the  former  remains  immovc- 

able. 


RESPIRATION. 


ii8 


Chap,  Vni. 


able.  For  tendons  are  but  little  changed  during 
inuibular  motion. 

ccLxiii.  The  ftruclure  of  the  parts,  and  the  dif- 
feclion  of  living  animals,  demonllrate,  that  the 
fieihy  portions  of  the  diaphragm,  by  afcending  on 
all  lides  from  fixed  points  to  middle  and  moveable 
parts,  deprefs  thefe,  and  by  that  means  draw  down- 
ward the  lateral  bags  (lxxvii.)  of  the  thorax, 
which  contain  the  lungs  *,  and  thus  augment  the 
perpendicular  diameter  of  the  breaft.  The  muf- 
cular  portions  are  more  depreffed  ; the  tendon  lefs, 
both  becauie  it  is  fixed  to  the  pericardium,  and 
becaufe  its  own  fubftance  does  not  contract.  The 
cefophagus  and  even  the  vena  cava  are  compreffed, 
while  the  diaphragm  acts.  The  diaphragm  almoft 
alone  performs  the  oflice  of  rcfpiration  in  a healthy 
man  who  is  at  reft  ; and  alfo  in  thofe  whofe  ribs 
are  fractured,  or  the  fternum  burft,  or  where  the 
perfon  will  not  make  ufc  of  his  ribs  on  account  of 
pain.  The  force  of  the  diaphragm  alfo,  in  dilating 
the  breaft,  is  greater,  according  to  calculation,  than 
all  the  reft  of  the  powers  which  contribute  to  ref- 
piration.  The  extent  of  an  infpiration  is  thus  far 
limited,  becaufe,  during  the  extreme  action  of  the 
diaphragm,  the  lovcer  ribs  are  drawn  inwards,  and 
the  breaft  is  fo  far  ftraitened.  To  oppofe  this,  the 
intercoflal  niufclcs  interfere  in  a moderate  infpi- 
ration j in  an  exceflive  one  they  are  not  equal  to 
the  diaphragm.  The  phrenic  nerve,  when  irrita- 
ted, more  evidently  than  in  moft  other  mufcles, 
forces  the  diaphragm  to  perform  its  office.  The 
lungs  themielves  are  entirely  governed  by  the  air, 
ribs,  and  diaphragm  ; being  in  immediate  contact 
with  thefe,  as  appears  through  a large  incifion,  or 
through  the  pleura,  or  pellucid  part  of  the  dia- 
phragm, when  the  containing  parts  remain  en- 
tire. 

ccLxiv.  In  violent  infpirations,  occafioncd  by 
an  increafed  quantity  of  blood  driven  into  the 

lungs, 


Chap.  VIH. 


RESPIRATION. 


I If 

lungs,  or  by  any  obftacle  occuriiig  in  them,  fcveral 
other  powers  elevating  the  thorax,  allift  in  dilating 
the  breaft,  which  are  inferted  into  the  thorax,  cla- 
vicles, or  fcapultE ; fuch  as  the  fcaleni  mufcles, 
malloidei,  trapezii,  cervicales  defcendentes,  ferrati 
fuperiores,  peclorales,  and  levatores  parvi,  for  which 
anatomy  mull  Ijp  confulted. 

ccLXv.  Thus,  there  are  powers  which  increafe 
the  capacity  of  the  thorax  in  all  its  three  diinen- 
lions  (ccLxiii.  and  cclix.)  By  thefe  the  cavity 
of  the  breaft  is  dilated,  fo  that  it  compreftes  the 
lungs  lefs  than  before  ; into  that  fpace  the  lungs 
ftrive  to  extend  themfelves,  ftnce  they  are  never 
deftitute  of  air,  which,  as  foon  as  the  preffure  is 
taken  off,  becomes  rarefied,  and  expands  itfelf. 
Independent  of  the  action  of  the  mufcles,  the  lungs 
poftefs  no  peculiar  inherent  power  of  attracting  air  ; 
and,  even  when  they  are  moft  full  of  air,  on  clofing 
the  trachea,  the  animal,  however,  attempts  to  in- 
fpire,  by  the  efforts  of  its  intercoftal  mufcles  and 
diaphragm.  It  follows,  that  the  air  (ccxlvii.) 
gravitating,  and  preffed  on  all  fides  by  the  incum- 
bent columns  of  the  atmofphere,  rnuft  enter  the 
thorax ; and  with  greater  force  the  lefs  air  is  in 
the  lungs  ; and  with  the  greateft,  if  they  contain  no 
air  ; but  air  will  not  enter  the  thorax,  if  the  air, 
beinsj  admitted  to  the  lurms  throusfh  a wound  in  the 
breait,  comprefs  their  iurface.  In  this  action, 
therefore,  which  is  called  infpiration,  the  bronchia 
are  every  way  increafed,  both  in  length  and 
breadth ; becaufe  all  the  diameters  of  the  thorax 
are  increafed,  and  the  inftated  lungs  remain  imme- 
diately contiguous  to  the  pleura.  At  the  fame 
time,  the  veffeis,  which  are  joined  with  the  bron- 
chia by  a cellular  flieath,  becomie  longer  and  are 
extended,  and  the  fmall  angles  become  larger;  by 
which  means,  the  circulation  is  facilitated.  Be- 
lides,  when  the  veficular  fubftance  of  the  lungs  is 
hiied  with  air,  the  ipace  through  which  the  capil- 
lary 


120 


RESPIRATION. 


Chap.  VIII. 


lary  veflels  of  the  hangs  run,  is  increafcd,  the 
branches  of  the  arteries  and  veins  are  ftretcKcd  out 
at  greater  angles,  the  lobes  prefs  lefs  upon  each 
other,  the  comprefilon  of  the  neighbouring  parts  is 
JefTened,  and,  therefore,  the  blood  fent  from  the 
heart  will  ilow  with  greater  eafe  and  celerity 
through  the  large  and  fmall  arteries  of  the  lungs. 
Hence,  by  inflating  the  lungs,  and  by  that  means 
facilitating  the  paflage  of  the  blood  to  the  left  ven- 
tricle, moribund  animals  are  refufeitated,  and  in 
the  fame  way  perfons  who  are  taken  out  of  the 
water  apparently  drowned.  But,  on  account  of  its 
great  levicy,  tlio  preiTure  of  tlie  air  upon  the  blood 
does  not  deferve  notice,  as  being  three  hundred 
times  iefs  than  the  force  of  the  lieart  ; and  in- 
jiifiicient  to  force  the  air  againft  the  blood,  M'hich 
may  eafily  be  done  by  a lyphon. 

CCLX7I.  Is  air  contained  between  the  lungs  and 
the  thorax  ? Is  this  air  rarciied  in  infplration,  and  af- 
terwards becoming  condenfed,  and  comprdTing  the  - 
lungs,  does  it  caufc  exfpiration  ? Is  this  opinion  con- 
firmed by  the  analogy  of  birds,  of  which  it  is  firicl- 
ly  true  ? Every  thing  concurs  to  confute  this  opin- 
ion : bcliir.d  the  pleura,  in  living  quadrupeds,  as 
well  as  in  dead  human  bodies,  llic  naked  lungs  arc 
^ vifible,  v.'idiout  any  intermediate  fpace  betwixt 
them  : on  perforating  the  pleura,  the  lungs  retract 
themfelves  towards  the  vertebrae,  as  foon  as  the  air 
conies  in  contact  with  them.  In  birds,  the  lungs, 
being  pervious,  admit  the  air  tlirough  large  holes 
into  the  caiity  of  the  thorax.  But  in  thefe  there 
is  a rnanifeit  fpace  betwixt  the  lungs  and  the 
pleura,  which  would  be  equally  manifeft  in  quad- 
rupeds, if  the  lungs  were  not  contiguous  with  the 
pleura.  Large  wounds,  admitting  the  air  into  one 
cavity  of  the  thorax  only,  dirninifli  the  rel'piration  ; 
but  fuch  wounds,  as  let  the  air  into  both  cavities, 
fupprefs  it.  When  the  thorax  i:/  opened  under 
v/ater,  it  emits  no  bubbles  of  air  ilu'ough  the  faid 

water  j 


Chap.  VIII. 


RESPIRATION. 


I2I 


water  ; but  in  birds,  in  whofe  thorax  there  is  air, 
it  does.  The  imaginable  fpace  betwixt  the  lungs 
and  the  thorax  is  filled  by  vapour,  or  a very  little 
water.  Adhefions  of  the  lungs  injure  the  refpira- 
tion  but  in  a fmali  degree  ; which  ought  entirely 
to  ceafe,  if  any  intermediate  air  betwixt  the  lungs 
and  thorax  were  neceffary  to  refpiration.  Finally, 
the  external  air,  being  admitted  to  any  of  the  m.em- 
branes  of  the  human  bodp,  infiames  them,  if  they 
be  not  defended  by  plentiful  mucus,  and  of  this  the 
pleura  is  deftitute. 

ccLxvii.  Refpiration,  whether  by  the  admix- 
ture of  a fubputrid  vapour,  or  in  fome  other  way, 
certainly  vitiates  the  air,  and  renders  it  unfit  eith- 
er for  inflating  the  lungs  or  fupporting  flame  ; 
and  laflly,  it  deprives  that  element  of  its  elafticity. 
It  is  probable  that  this  happens  from  putrefaction, 
fince,  by  a crowd  of  men  the  air  is  rendered  pefli- 
lenti^,  and  fevers  of  the  molt  malignant  kind  are 
generated  in  a few  hours.  In  whatever  way  it  hap- 
pens, we  are  certain,  that,  in  the  lungs,  the  air  is 
vitiated  ; lofes  its  elafticity  ; and  cannot  keep  the 
lungs  diftended,  fo  as  to  tranfmit  the  quantity  of 
blood  now  increafed  by  the  dilatation  of  the  pul- 
monary arteries,  into  the  veins.  Nor  can  the  wdll 
dilate  the  breafl;  beyond  certain  bounds,  or  aflift  the 
pafiage  of  the  blood.  A ftate  therefore  wall  take 
place,  in  which  the  blood  cannot  pafs  through  the 
lungs. 

ccLxviH.  Thus  a nev/  refiflance  to  the  blood  con- 
tinually coming  from  the  heart  is  generated  : and 
in  long  retentions  of  the  breath,  as  in  making  vio- 
lent efforts,  the  venous  blood,  efpecially  of  the  head, 
flagnates  before  the  right  ventricle  of  the  heart, 
which  is  clofed  up,  becauie  it  cannot  evacuate  it- 
felf  into  the  lungs  ; and  tumefies  the  face  with  red- 
nefs,  and  fomietimes  burfts  the  veins  of  the  brain, 
neck,  intellines,  kidneys,  or  lungs,  and  even  the 
right  auricle  of  the  heart.  This  is  the  caufe  of 

exceffive 


1^2 


RESPIRATION. 


Chap.  VIII. 


excellive  anxiety  of  mind  ; this  is  the  caufe  of  death 
in  compreffed  air,  in  perfons  drowned  or  ftrangled, 
which  is  much  more  hidden  than  is  commonly  im- 
agined v/ith  regard  to  drowned  people.  A living 
perfbn  therefore,  that  he  may  remove  thofe  incon- 
veniencies  which  arife  from  the  palfage  of  the 
blood  being  ouftructed,  Ilackens  the  powers  of  in- 
fpiration,  and  excites  to  action  thofe  of  exfpiration, 
in  order  to  free  the  breaft  from  the  too  greatly 
rarefied  air. 

cci>xix.  Thefe  powers  are,  firft,  the  elafticity  of 
the  ribs,  which  being  drawn  upwards  out  of  their 
natural  fituation,  as  foon  as  the  elevating  powers 
eeafc  to  acf,  fpontaneoully  replace  therafelves  at 
more  acute  angles  with  the  fternum  and  vertebrae. 
There  is  alfo  the  claftic  force  of  the  bronchia  and 
veficles  diftended  with  air,  by  which  they  endeav- 
our to  contract.  Elence  exfpiration  is  performed 
more  eafily  and  quickly  than  infpiration  j and  hence 
it  is  the  lail  acition  of  dying  people. 

ccLxx.  Thefe  are  alTiited  by  the  abdomdnal  muf- 
cles  ; the  oblique,  Itraight  and  tranfverfe.  The 
former  of  thefe  are  faftened  by  one  part  to  tlie 
lower  ribs  ; and  by  another  part,  they  are  attached 
to  the  os  pubis  and  ilium,  which  are  immoveable, 
v/hen  compared  with  the  breaft.  Therefore,  t-ic 
ftraight  mufcles,  being  contracted,  flatten  the  arcli 
into  which  the  abdominal  vifeera  were  protruded 
by  the  depreflion  of  the  diaphragm,  reduce  tlie  con- 
vexity of  the  abdomen  nearer  to  a ftraight  line ; 
force  the  abdominal  vifeera  up^rards  and  backwards 
againft  the  diaphragm,  which  alone  can  give  way  ; 
and  prefs  it  up  into  the  thorax,  v'hich  is  thus  ren- 
dered fliorter.  The  oblique  mufcles,  for  the  fame 
reafons,  comprefs  the  lateral  parts  of  the  abdomen, 
carry  the  liver  and  ftomach  backwards,  and  prefs 
them  towards  that  place  vEere  there  is  the  Icaft 
rcflftance.  Laftlv,  all  of  them  draw  down  the  ribs 
which  \vere  elevated  by  the  intercoftals.  The 

trantieiTe 


Chap.  VIII. 


RESPIRATION. 


tranfverfe  mufcles,  indeed,  do  not  draw  down  the 
ribs  ; but  they  pull  the  cartilages  of  the  falfe  ribs 
a little  inwards,  render  the  whole  abdomen  much 
narrower,  and  force  the  fame  vifcera  againft  the 
diaphragm.  As  acceiTory  powers  may  be  reckoned 
the  fternocoftal,  and  the  long  internal  intercoftal 
mufcles,  which  are  called  depreffors.  By  this  joint 
force  the  elevated  ribs  defcend  ; the  middle  ones 
more,  the  uppermoft  lefs,  the  loweft  moft  of  all ; 
their  margins  are  drawn  inwards  : the  cartilages 
afcend,  and  return  into  acute  angles  with  the  fter- 
num  5 and  the  fternum  itfelf  recedes  backv/ards 
with  the  ribs.  By  thefe  means  the  thorax,  by  the 
converfe  of  cclix.  is  rendered  narrower  in  every 
direftion  and  fhorter,  and  expels  as  much  air  out 
of  the  lungs  as  is  faihcicnt  to  remove  the  uneah- 
nefs  (ccLxviii.) 

ccLXXi.  In  violent  refpiration,  when  the  infpira- 
tions  are  fuller,  the  more  powerful  expirations  de- 
rive afliftance  from  fome  other  caufes,  as  the  facro- 
lumbalis,  longiffimus  and  quadratus  mufcles.  By 
this  force,  leaden  bullets,  weighing  above  a dram, 
may  be  blown  to  the  diftance  of  363  feet ; which 
force  is  equal  to  a third  part  of  the  preffure  of  the 
atmofphere.  But,  in  a healthy  perfon,  the  mufcles 
of  the  abdomen  alone  faflice,  and  the  lunns  are  not 
fo  much  emptied  as  in  blowing. 

ccLxxii.  The  effects  of  exfpiration  are  the  com- 
preflion  of  the  blood- veffels  of  the  lungs  ; the  dimi- 
nution of  the  angles  of  the  bronchia ; the  reitino- 
the  weight  of  the  adjacent  veffels  on  the  reticular 
veffels  ; the  expulfion  of  the  corrupted  air  from  the 
lungs  ; the  propulfion  through  tlie  veir.s  of  that 
part  of  the  blood  which  is  impacted  in  the  capil- 
lary arteries,  to  the  left  fide  of  the  heart,  and  the 
impeding  that  part  of  the  blood  which  is  coming 
from  the  right  ventricle.  Exfpiration,  therefore, 
flops  the  ready  entrance  of  the  blood  into  the  lungs ; 
and  as  the  \vhole  thorax  is  cornpreifed  at  the  fame 

time^ 


124 


RESPIRATION. 


Chap.  MU. 


time,  it  repels  the  venous  blood  into  the  veins  of 
the  head,  and  nils  the  brain  and  its  finufes. 

cci,xxiii.  In  this  manner  the  necefuty  for  refpi- 
ration  arifes  anew,  as  often  as  the  collapfed  vellels 
of  the  lungs  relilf  the  blood  expelled  from  the  right 
ventricle  of  the  heart : this  is  one  caufe  of  death 
in  thofe  animals  which  expire  in  velTels  exhaulled 
of  air.  The  lunes  in  thole  which  have  remained 
long  in  vacuo,  from  having  the  air  drawn  out  from 
them,  become  denfe,  folid,  and  heavier  than  water  ; 
and,  therefore,  impervious  to  the  blood.  Of  the 
fame  kind  is  the  death  of  thofe  who  are  killed  by 
lightning,  and  perhaps  by  the  noxious  vapours  of 
caverns.  Therefore,  in  confequence  of  a moll  in- 
telligent ftruclure,  at  the  hrft  perception  of  the  un- 
eafinefs  ariling  from  the  oppofition  to  the  paffage 
of  the  blood  through  the  lungs,  the  exfpiring  pow- 
ers become  relaxed,  the  infpiring  powers  are  ex- 
cited into  action,  and  the  motion  of  the  blood 
through  the  lungs  is.  rendered  free  and  accelerated. 

ccLxxiv.  Are  there  other  caufes  of  alternate 
refpiration  ? Is  any  thing,  to  be  derived  from  the 
compreffion  of  the  vena  fine  pari,  of  the  plirenic 
nerve,  or  from  the  blood  not  being  fent  to  the 
brain  ? But  thefe  are  difproved  by  comparative 
anatomy  ; which,  where  there  is  no  fuch  nerve  or 
vein,  finds  the  fame  alteration  in  refpiration  every 
where.  Does  it  proceed  from  the  alternate  con- 
tradlicn  of  antagoniil  mufcles,  among  vTdch,  thofe 
of  exfpiration  relax  thofe  of  infpira-tion,  and  the 
reverfe  ? But,  according  to  this  argument,  aU  the 
jnufcles  of  the  hum.an  body  would  be  perpetually 
alternating  in  their  motions. 

ccLxxv.  From  what  has  been  faid,  it  fufficiently 
appears,  that  refpiration  is  abfolutely  neceffary  to 
a healthy  adult  ; becaufe,  whether  the  lungs  re- 
main long  in  a Hate  either  of  exfpiration  or  of 
jnfpiratioii  (cclxxiii.  cci^viii.)  death  will  be  the 

confequence. 


Chap.  VnL 


IRESPIRATION. 


i-25 


confequence.  Therefore,  no  animal,  that  lias  lungs 
like  ourfelves,  after  it  has  breathed  for  forne  time, 
fo  that  the  air  ihall  have  penetrated  into  the  in- 
Inoft  parts  of  the  lungs,  and  the  pulmonary  artery 
fliall  have  brought  a new  quantity  of  blood  to  that 
vifcus,  can  fubfift  longer  than  a few  minutes  with- 
out the  ufe  of  air,  without  perifliing,  or  at  lead: 
falling  into  a ftate  which  differs  from  death  only  in 
the  poffibility  of  recovery.  In  an  animal  recently 
born,  this  neceffity’for  air  does  not  take  place  very 
inftantaneoufly. 

ccLxxvi.  But  the  ufe  of  refpiration  Is  different 
from  this  necefGty ; which  nature  might  have  avoid- 
ed, either  by  forming  no  lungs  at  all,  or  by  con- 
ftruftiiig  them  fimiiar  to  thofe  of  the  fetus.  The 
ufe,  therefore,  of  refpiration,  muft  be  very  confid- 
erable,  fince  all  animials  are  furniflied  either  with 
lungs,  or  with  gills,  or  with  a windpipe  diftributed 
through  all  parts  of  the  body. 

ccLxxvii.  To  inveftigate  this  utility,  let  us  com- 
pare the  blood  of  the  adult  with  that  of  the  fetus, 
and  with  the  vital  ftuid  in  fillies.  It  appears,  that  in 
the  foetus  the  blood  is  deftitute  of  its  fiorid  rednefs 
and  folid  denfity  ; that  the  blood  of  filh  is  cold, 
and  has  lefs  denfity,  and  a tender  craffamentum.  It 
is  therefore  probable,  that  the  blood  acquires  both 
thefe  properties  in  tlie  lungs. 

ccLxxviii.  Is  animal  heat  generated  principally 
in  the  lungs  ? Does  it  arife  from  the  alternate  ex- 
tenfion  and  contraftion,  relaxation  and  compreffion, 
of  the  veflels  (cclxv.  and  ccuxxii.)  by  which  the 
folid  parts  of  the  blood  are  perpetually  rubbed  to- 
gether, and  fuu'er  attrition  from  their  conftriftion  ? 
Ihe  lungs,  therefore,  will  add  to  the  office  of  the 
reft  of  the  arteries,  becaufe  in  them  the  blood  is  al- 
ternately relaxed  and  comprexTed  more  than  in  any 
other  part  of  the  body.  But  when  the  lungs  are 
obflrufted,  ulcerated,  and  ahnoft  deftroyed,  morbid 
heat  is  increafeci  in  the  human  body ; and  in  the 

lungs^ 


RESPIRATION. 


1:26 


Chap.  VIII, 


lungs,  the  cold  air  comes  moil  nearly  in  contact 
with  the  blood. 

ccLXxix.  The  deniity  is,  indeed,  promoted  by 
the  copious  difcharge  of  watery  vapour  from  the 
VelTels  of  the  lungs,  by  which  the  reft  of  the  m.afs 
becomes  fpscifically  heavier.  In  the  fame  manner 
as  in  other  arteries,  the  blood,  being  alternately  re- 
tarded and  accelerated,  is  figured  by  the  moulds  of 
the  ultimate  arteries,  becomes  fpherical,  and  there- 
fore denfer,  having  more  ponderous  globules,  and 
iefs  light  fluid.  I’he  pulmonary  vein  alfo  being 
fmaller  than  its  correfponding  artery,  is  of  confider- 
able  ufe  in  compreffmg  the  globules,  and  in  increaf- 
ing  their  attraction.  Neverthelefs,  cold  animals, 
with  very  fmall  lungs,  have  denfe  and  coagulable 
blood  ; as  alfo  the  chick  in  ovo.  The  courfe  of 
the  blood  through  the  lungs  is  fhortcr  : through  the 
whole  body  the  courfe  is  longer,  and  the  artery 
weaker  ; the  ventricle,  by  wdiich  the  blood  is  pro- 
pelled, is  aifo  weaker. 

ccLxxx.  Is  the  air  itfelf  received  into  the  blood 
in  the  lungs,  and  docs  it  there  produce  neceflary 
vibrations  ? Is  this  demonftrated  from  the  refiftance 
of  the  body  to  the  weight  of  the  external  air  ; from 
the  air  found  in  the  biood-vcfiels,  in  the  cellular 
fubftance,  and  in  the  cavities  of  the  human  body  ; 
from  the  cracking  produced  by  extending  the  joints ; 
from  air  being  manifeftly  poured  from  the  trachea 
into  the  hearts  of  many  animals,  as  thelocuft  ; from 
the  cfcape  of  air  from  the  blood  and  animal  fluids 
in  Mr.  Boyle’s  vacuum  ; from  the  necefllty  of  a 
\utal  ofeiilation  in  the  blood  ; and  from  the  increaf- 
ed  rednefs  of  the  pulmonary  blood  ? 

ccLxxxi.  That  no  elaftic  air  is  here  received  in- 
to the  blood,  is  demonftrated  from  its  not  being 
able  to  enter  into  the  blood,  if  it  retain  its  elaftici- 
ty  ; from  the  inutility  of  its  reception,  if  its  elafti- 
city  be  loft  in  the  blood  ; from  the  perfecT  immu- 
tability ox  the  blood  by  cold  ; from  the  minuteneft 


Ghap.  VIII. 


RESPIRATION. 


t'l’] 

of  the  inhaling  velTels  ; from  the  lides  of  the  veiides 
being  perpetually  covered  with  mucus  ; from  the 
elaftic  nature  of  air  being  unfit  to  pafs  through  ca- 
pillary veffels  ; and  from  its  repulfion  by  water, 
that  hinders  it  from  paffing  through  moiftened  pa- 
per, linen,  or  leather.  Again,  air  thrown  into  the 
trachea  never  pafi’es  'into  the  heart ; or  only  when 
it  is  driven  with  exceffive  force.  In  the  veffels  and 
humours  of  the  human  body,  air,  from  a ftate  of  in- 
elafticity,  becomes  elaftic  in  confequence  of  putre- 
fadion,  froft,  or  an  external  vacuum.  But  fuch  air 
exifts  in  every  liquid,  and  is  taken  into  our  bodies 
with  the  aliments,  and  with  vapours,  mixing  flowly 
and  difficultly.  There  never  were  any  elaftic  bubbles 
of  air  obferved  in  the  blood  of  a living  animal,  un- 
lefs  after  wounds  ; air  being  inSated  into  the  blood- 
veffels  of  any  animal,  kiUs  it  certainly  and  fpeedily. 
Nor  is  there  any  thing  fufficiently  certain  in  the  in- 
creafed  rednefs  of  the  blood  in  the  pulmonary  veins.- 
Laftly,  air  indeed  is  abforbed  by  moft  fluids,  and  by 
water,  but  flowly,  and  only  at  the  end  of  feveral 
days  after  the  former  air  has  been  exhaufted  by  the 
pump.  It  then  likewife  lays  aftde  its  elaftic  nature  ; 
and  no  reafon  has  been  advanced  why  the  air  lliould 
either  be  more  fpeedily  abforbed  by  the  blood,  or 
why  it  fliould  retain  its  elafticity  after  its  abforp- 
tion. 

ccLxxxii.  Is  the  blood  cooled  in  the  lungs  ? Is 
this  proved  from  the  death  of  animals  in  air  heated 
to  the  fame  degree  with  the  animal,  as  is  believed 
to  have  happened  from  very  fultry  fummer  weath- 
er, and  fcorching  eaft  winds  ? Are  the  pulmonary 
veins,  therefore,  lefs  than  the  arteries  ? Does  the 
deftre  of  cold  in  hard  working  people  arife  from 
thence  ? That  the  blood  is  cooled  in  the  lungs,  is 
thus  far  true,  that  it  warms  the  contiguous  air,  and 
therefore  imparts  to  it  fomething  of  its  own  heat. 
But  that  this  was  not  the  defign  of  nature,  is  evi- 
dent \ ftnee  no  one  has  faid,  that  the  venous  blood 

is 


128 


RESPIRATION. 


Chap.  VIIL 


is  hotter  than  the  arterial,  although  fome  affert  that 
it  is  colder ; and  nobody  ever  obferved  the  left  ven- 
tricle of  the  heart  colder  than  the  rig^ht.  But  the 
venous  blood  enters  the  luns^s.  If  it  be  cooled 
there,  it  follows  that  the  arteries  muit  receive  it 
ftill  colder.  Therefore,  the  blood  recovers  that 
heat  which  it  lofc,  and  even  niore  : and  bdides,  a 
perfon  may  live  in  an  air  much  hotter  than  the 
blood  itfeif,  of  which  we  have  a familiar  example 
in  baths,  and  warm  climates.  The  fize  of  the 
pulmonary  artdry  in  the  foetus,  which  does  not  re- 
Ipire,  is  greater  j and  the  larger  area  of  the  right 
auricle  and  ventricle  of  the  heart,  which  is  likewife 
much  greater  in  the  foetus,  feems  to  be  a receptacle 
fubfervient  to  frequently  neceiTary  retardations,  and 
the  narrowneis  of  the  vein  contributes  to  the  accel- 
eration of  the  blood. 

ccLxxxiii.  Does  the  blood  derive  its  rednefs  from 
the  air  ? This  is  contradicted  by  what  we  fee  in 
cold  animals,  which,  though  they  make  aimoft  no 
ufe  of  the  air,  have  blood  equally  red  with  that  of 
warm  animals  ; by  the  certain  connection  of  red- 
nefs in  the  blood  of  frogs,  with  their  having  plenty 
of  food,  and  of  paleneis  with  want  of  food ; and 
by  the  air,  as  we  have  jufc  now  faid,  having  no  ac- 
cefs  to  the  blood.  Neverthelefs,  rednefs  is  produ- 
ced, and  reftored  to  the  blood  by  the  contact  of  air, 
and  is  deftroycd  by  its  removal.  Does  fomc  fubtle 
element  from  the  air  penetrate  the  blood,  and  caufe 
its  colour,  as  light  is  required  for  the  colours  of 
plants  ? 

ccLxxxiv.  Is  the  ufe  of  the  lungs,  to  abforb 
nitre  from  the  air  to  the  blood  ? Is  this  the 
caufe  of  the  florid  colour,  obfervable  on  the  furface 
of  a cake  of  blood,  while  the  bottom  part  is  black. 
Does  this  preferve  the  animal  from  putrefaction  ? 
It  is  certain,  that  fome  volatile  principle  of  acidity 
exifts  in  the  air,  which,  with  a luitable  earth,  forms 
nitre  j for  nitrous  earth,  after  being  exhaufted, 

when 


Chap.  VIIL  RESPIRATION;  ' 129 

when  expofed  again  to  the  air,  becomes  reimpreg- 
nated with  nitre.  But  the  fame  principle  of  acid- 
ity, we  kno\X"  by  certain  experiments,  with  differ- 
ent earths,  forms  a vitriolic  fait,  or  alum,  or  fea- 
falt.  For  the  caput  mortuum  of  fea-falt,  which, 
remains  after  the  dillillation  of  the  acid,  recovers 
from  the  air  the  property  of  furniiliing  more  acid 
by  dillillation  ; and  in  fnow,  there  is  cubical  fait  i 
from  marcafites,  true  vitriol  exudes ; and  colco- 
thar  recovers  the  acid,  which  was  drawn  from 
it,  and  alkali  becomes  vitriolated  tartar.  Is  this, 
therefore,  the  ufe  of  refpiration  ? The  quantity  of 
thefe  falts,  which  exifts  in  the  air,  is  too  fmall ; and 
refpiration  ismoft  falutary  on  the  higheft  mountains, 
where  they  are  moft  rare  ; nor  have  any  m^arks  of 
a nitrous  fait  ever  been  detefted  in  our  blood. 

ccnxxxvi.  Why  do  tortoifes, frogs, lizards, fnailsj 
earwigs,  and  many  other  infedlsj  live  long  without 
air  ? In  them,  the  lungs  arc  given;,  not  fo  much  for 
the  preparation  of  the  blood,  of  which  they  have 
but  a iinall  quantity,  as  for  affifting  them  in  fwim- 
ming  ; hence  their  lungs  are  fuppiied  with  veins 
from  the  cava,  and  with  arteries  froHi  the  aorta^ 
Infects  inhale  and  exhale  air,  through  points  in  the 
fkin.  Why  do  ail  animals,  however  fmall,  fucli  as 
little  birds,  periflr  in  air  that  is  not  renewed  ? Be- 
caufe  the  air,  which  has  once  entered  the  lungs,  is 
contaminated  by  inelaftic,  watery,  and  alkaline  va- 
pours, and  therefore  it  becomes  noxious  1 not  be- 
caufe  it  becomes  lighter  ; for  the  mercury  falls  but 
little  in  air,  which  has  not  been  renewed,  and  which 
has  killed  an  animal.  Hence,  on  the  other  hand, 
animals  furvive  loiter  in  air  which  is  more  com- 
prelfed  than  that  or  the  atmofphere" ; for  in  that 
cafe,  the  proportion  of  the  elaftic  element  is  great- 
er, and  therefore  the  air  isTnore  fiowly  contami- 
nated. But,  even  in  other  cafes,  confined  air  becomes 
deleterious,  and  filled  with  vapours,  by  ftagnation 
alone.  Vv^hy  do  animals  fweii  in  an  exhaufted  re- 
R ceiver  ? 


RESPIRATION. 


150 


Chap.  VIII. 


ceiver  ? From  the  expanfion  of  the  air,  which  ex- 
ifted  in  an  inelaftic  ftate  in  the  blood. 

ccLxxxvii.  There  is  a certain  connexion  be- 
tween the  pulfe  and  refpiration.  According  to  the 
common  cmirfe  of  nature,  three  or  four  pulfations 
are  reckoned  to  one  refpiration.  If  the  quantity  of 
blood  fent  to  the  heart  be  increafed,  the  frequency, 
both  of  the  puhe  and  refpiration,  are  increafed. 
This  is  the  reafon  of  the  panting  in  a perfon,  tak- 
ing exercife,  vchich  accelerates  the  motion  of  the 
venous  blood  (cxlii.)  If  the  blood  meet  with 
much  refiftance  in  the  lungs,  and  do  not  pafs  freely 
from  the  right  into  the  left  ventricle  of  the  heart ; 
to  accelerate  its  courfe,  both  the  number  and  mag- 
nitude of  the  refpirations  are  increafed.  This  is  the 
caufe  of  fighing,  yawning,  and  panting  ; of  which 
the  firft  is  a deep  infpiration  ; the  fecond  flow,  and 
very  great ; and  the  third,  frequent  and  imperfeef. 
The  number  of  refpirations,  however,  does  not  al- 
vrays  increafe  with  the  pulfe  ; of  which  vee  have  an 
example  in  fevers,  in  which  the  lungs  are  not  af- 
fefeed. 

ccLxxxviii.  The  mucus,  which  lines  the  fcnflblc 
membrane  of  the  bronchia,  may  become  trouble- 
fome,  both  by  its  quantity  and  acrimony  ; it  has 
been  even  known  to  caufe  fuffocation  in  a dropfy 
of  the  lungs.  Therefore,  its  fuperabundance,  adhe- 
fion,  or  acrimony,  is  removed  by  coughing  ; name- 
ly, by  irritating  the  refpirative  fyftein,  the  mucus 
or  concretions  are  loofened  and  expelled  by  large- 
infpirations,  and  exfpirations,  alternately  fucceed- 
ing  each  other  with  rapidity,  and  by  ftrokes  of  the 
abdominal  mufcles. 

ccLxxxix.  Laughter  diners  from  coughing  in  its 
caufe,  which  refldes  commonly  in  the  mind,  or  at 
leaft  conliiLS  in  the  titillation  of  fome  of  the  cuta- 
neous nerves  ; and  ahb,  becaufe,  after  one  deep  in- 
fpiration, there  are  frequent  but  imperfecl:  exfpira- 
tions, through  the  contrafted  glottis,  and  the  air  is 

not 


Chap.  VIIL 


RESPIRATION. 


131 

not  totally  evacuated  from  the  lungs.  Hence  laugh- 
ter, in  a moderate  degree,  conduces  to  health  ; be- 
caufe,  in  place  of  one  full  infpiration,  fever al  infpi- 
rations  and  exfpirations  happen  in  the  fame  time, 
and  thus  the  concuffion  is  greater.  Hence  its  dan- 
ger, from  ftagnation  of  the  blood  ; becaufe  the  ex- 
Ipiration  is  not  full,  and  therefore  the  blood  is  ad- 
mitted into  the  pulmonaiy  artery,  but  is  not  fuffer- 
ed  to  pafs  through  it.  Weeping  begins  with  a deep 
infpiration,  after  which  follow  fhort  alternate  infpi- 
rations  and  exfpirations  5 and  it  is  finifhed  with  a 
deep  exfpiration,  which  is  immediately  followed 
by  an  infpiration  : hence  it  has  nearly  the  fame 
good  and  bad  effe6ls  ; and,  when  moderate,  it  re- 
lieves the  diflrefs  arifing  from  grief.  Hiccough  is 
a very  great,  fonorous,  and  fudden  infpiration. 
Sneezing  confifts  of  one  deep  infpiration,  fucceed- 
ed  by  a Angle  powerful  exfpiration  ; and  by  the 
torrent  excited,  the  acrid  matter,  irritating  the  nof- 
trils,  is  blown  away. 

ccxc.  The  fecondary  ufes  of  refpiration  are  very 
numerous.  It  exhales  copioufly,  and  removes  from 
the  blood  fomething  highly  noxious  ; for  by  remain- 
ing in  the  air,  it  will  caufe  fuffocation  ; and  the 
breath  of  many  people,  crowded  in  a clofe  and  fmali 
place,  impregnates  the  air  with  a fuffocating  quali- 
ty. On  the  other  hand,  it  abforbs  from  the  air  a 
thin  vapour,  of  which  the  ufe  is  perhaps  not  fuih- 
ciently  known.  It  is  alfo  a force,  which  perpetu- 
ally Gompreffes  the  abdomen,  and  all  its  vifeera  ; it 
evacuates  the  ftomach,  inteftines,  gaU  bladder,  re- 
ceptacle of  the  chyle,  urinary  bladder,  inteftinum 
re6tum,  and  the  womb ; it  comminutes  the  aliments, 
and  forces  the  blood  through  the  liver,  fpleen,  and 
mefentery.  It  caufes  a kind  of  flux  and  rehux  in 
the  blood,  fo  that  it  is  alternately  prelfed  back  to- 
wards the  extremities  of  the  veins,  and  a little  af- 
ter is  propelled  towards  the  heart  by  an  accelerated 
velocity,  as  into  an  empty  fpaee.  Moreover,  infpi- 
k 2 ration 


tp  VOICE  AND  SPEECH.  Chap.  IX. 

ration  attracts  the  odoriferous  particles  from  the 
air,  and  conveys  them  to  the  fenforiuin.  But  even 
fucking,  fo  necelfary  to  the  new  born  infant,  is  ef- 
fected by  infpiration,  and  by  forming  a larger  fpace, 
in  which  the  air  contained  in  the  mouth  is  rare- 
fied, fo  that  the  prelTure  of  the  external  air  forces 
the  milk  into  that  part  where  it  is  leaft  refifted. 
Eaftly,  the  voice  itfelf  depends  upon  the  air,  and 
feems  to  be  the  principal  manifeft  effect  of  refpira- 
tion.  This,  therefore,  appears  a proper  opportuni- 
ty for  defcribing  it. 


C H A P.  IX. 

VOICE  AND  SPEECH. 

ccxci.  ^ I 'HE  principal  organ  of  the  voice  is  the 
I larynx ; for,  when  it  is  injured,  the 
air  paffes  through  the  windpipe,  without  yielding 
any  found.  By  the  larynx,  we  underhand  an  af- 
femblage  of  cartilages,  joined  into  a hollow  ma- 
chine, which  receives  the  air  from  the  fauces,  and 
tranfmits  it  into  the  windpipe,  connected  with  it  by 
ligaments  and  mufcular  fibres.  Among  the  larger 
of  thefe  cartilages,  the  annular  and  fcutiform  in 
adults  offify  internally.  The  anterior  and  larger 
part  of  the  larjmx,  which  lies  almolt  immediately 
under  the  Ikin,.  is  compofed  of  two  cartilages  ; the 
thyroid  and  cricoid,  to  which  the  lateral  parts  of 
the  larynx  alfo  belong  in  fuch  a manner,  that  the 
portions  of  the  cricoid  cartilage  always  become 
larger,  as  they  are  higher  feated.  The  back  part  of 
the  larynx  is  compofed  firff  of  the  faid  annular  car-^ 
tilage,  and  afterwards  of  the  ai*ytenoid  cartilages, 
connecled  by  mufcles.  The  epiglottis,  loofely  con- 
nected with  the  thyroid  cartilage,  is  either  raifed 
or  inclined  over  the  larynx.  The  veffels  arife  from 
the  upper  and  lower  thyroids  j the  nerves  are  nu- 
merous ; 


Chap.  IX.  VOICE  AND  SPEECH. 


^33 

merous ; the  inferior  ones  come  from  the  recur- 
rents ; the  fuperior  ones  from  the  eighth  pair,  inof- 
culating  in  various  ways  ; fome  alfo  from  the  inter- 
coftal.  The  former  of  thefe  nerves  is  remarkable 
for  its  origin  in  the  thorax  ; for  its  reflection  round 
the  aorta  and  right  fubclavian ; for  its  giving  rife 
to  fome  of  the  nerves  of  the  heart,  and  for  the  ex- 
periment, which  proves,  that  the  voice  is  deftroyed, 
by  tying  this  nerve. 

ccxcii.  All  thefe  cartilages  are  connected  togeth- 
er by  various  mufcles  and  ligaments,  fo  that  the 
whole  may  poflefs  mobility,  while  fome  of  its  parts 
are  firm,  and  others  extremely  moveable.  The 
feutiform  or  thyroid  cartilage,  fituated  on  the  fore- 
part, is  compofed  of  two,  alm.oft  quadrangular 
plates,  inclined  to  each  other  in  an  obtufe  angle, 
projecting  forwards.  In  thefe  plates,  two  apertures, 
one  on  each  fide  for  the  internal  veflels  of  the 
larynx,  are  found  fometimes,  though  rarely.  The 
upper  procefles  of  this  cartilage,  terminating  in  a 
thick  point,  inclining  upwards  and  backwards,  are 
connected  with  the  horns  of  the  os  hyoides,  by 
ftrong  ligaments,  fometimes  mixed  with  bone.  The 
lower  procefles  are  ihortcr,  are  adapted  to  the  flight- 
ly  hollowed,  and  almofl:  fiat  furfaces  of  the  cricoid 
cartilage  ; and  are  connected  by  a very  firm  artic- 
ulation, on  account  of  the  fliortnefs  and  ftrength 
of  the  cellular  fubftance,  which  unites  them.  The 
middle  anterior  part  is  joined  by  ftrong  perforated 
ligaments,  to  the  m.iddle  of  the  annular  cartilage  ; 
and  likewife  by  other  fuperior  ligaments,  proceed- 
ing from  the  defeending  horn  of  the  feutiform 
cartilage,  to  the  upper  part  of  the  annular  carti- 
laa;e. 

O 

ccxciii.  The  cricoid  cartilage,  anteriorly  thick 
and  hard,  is  increafed  backwards,  in  form  of  a ring 
unequally  truncated ; and,  in  the  middle,  it  is  di- 
vided into  two  cavities  by  a protuberant  line.  It 
j-s  firmer  than  the  refl  of  the  cartilages,  and  forms 

their 


VOICE  AND  SPEECH. 


Chap.  IX. 


^34 


their  bahs.  From  it  longitudinal  mufcular  fibres 
and  ligaments  defcend  to  the  windpipe  (ccxxxviii.) 
The  pharynx  connecled  with  each  of  thefe  cartila- 
ges by  many  mufcular  layers,  receives  the  larjmx 
into  its  cavity.  From  this  cartilage  a fliort  liga- 
ment proceeds  to  the  arytenoid  cartilage  on  each 
fide. 


ccxciv.  The  fis'ure  of  the  two  arvtenoid  cartila- 

A-/  4 

ges  is  very  complex.  It  fpontaneoufly  divides  in- 
to two  parts,  of  which  the  lower  is  larger,  and 
is  connected  by  a moderately  concave  bafe  wdth  tlie 
thick  cricoid  cartilage,  forming  a moveable  articu- 
lation. It  fends  a procefs  forwards,  which  fepa- 
rates  the  glottis,  and  fuflains  the  inferior  part  of 
the  ventricle  of  the  larynx.  They  afcend  upwards, 
of  a triangular  figure  : the  pofterior  bafe  is  hollow, 
and  the  anterior  fide  is  convex,  and  divided  by 
three  furrows.  They  are  extenuated  upwards,  till 
they  are  at  lafi:  terminated  by  a pretty  thick,  oval, 
cartilaginous  head  fixed  on  them.  I'he  lower  part 
of  thefe  cartilages  is  connected  by  numerous  muf- 
cular  fibres,  partly  tianlverfe,  and  partly  oblique  ; 
of  which  the  different  directions  are  evident,  though 
they  cannot  be  feparated,  Thefe  are  called  the 
arytenoid  mufcles.  In  their  upper  part,  the  aryte- 
noid cartilages  are  feparated  by  a perpendicular 
chinlc,  which  has  been  improperly  by  fome  called 
the  Q'lottis. 

ccxcv.  The  arytenoid  cartilages  are  connected 
with  the  thyroid  by  tranfverfe  ligaments,  for  the 
molt  part  fufficiently  ftrong  and  elaftic,  but  cover- 
ed with  the  common  mucous  membrane  of  the  la- 
rynx. Thefe  ligaments  arife  below  the  middle  of 
the  arytenoid  cartilages,  and  are  inferted  into  the 
fiat  angle  of  the  thyroid  cartilage  (ccxcii.)  and 
may  be  feparated  from  each  other,  by  remoHng  the 
arytenoid  cartilages  from  being  in  mutual  contacf, 
apid  may  be  again  brought  into  contiguity'  by'  the 

cartilages 


Chap.  IX. 


VOICE  AND  SPEECH. 


135 

cartilages  approaching  each  other.  This  conftitutes 
the  true  glottis,  and  is  continuous,  but  at  right  an- 
gles with  the  above  mentioned  chink  (ccxciv.) 

ccxcvi.  From  the  fame  angle  of  the  thyroid  car- 
tilage, under  a notch,  from  a firm  ligament,  a car- 
tilage arifes,  with  an  ere£t  flender  ftalk,  of  an  oval 
flaape,  convex  before,  behind  cohcave,  and  with  its 
fuperior  extremity  reflefted  backwards  and  con- 
cave. It  is  kept  erect  by  its  own  elafticity,  fo  that 
it  rifes  upright  behind  the  tongue  ; but  it  can  be 
fo  inclined  whenever  the  root  of  the  tongue  is  preff- 
ed  backward,  that,  having  become  tranfverle,  it 
completely  fhuts  up  and  protedls  the  paffage  into 
the  larynx,  which  defcends  between  this,  the  epi- 
glottis, and  the  arytenoid  cartilages.  The  epiglot- 
tis is  joined  to  the  tongue  by  pale  m.embranous  fi- 
bres, and  to  the  os  hyoides  by  much  membranous 
expanfion.  It  either  has  no  fibres  from  the  thyroj 
arytenoidal  and  arytenoidal  mufcles,  or  they  are 
too  minute  to  counteracf  its  elaflicity. 

ccxcvii.  At  the  fides  of  the  lioaments  of  the 
glottis  (ccxcv.)  two  other  upper  and  fofter  liga- 
ments, lefs  tendinous  or  elaflic,  proceed  parallel 
from  each  arytenoid  cartilage  to  the  thyroid.  Be- 
twixt thefe  two  (ccxcvii.  and  ccxcv.)  ligaments  of 
each  fide,  a peculiar  cavity  or  ventricle  defcends, 
having  the  figure  of  a compreffed  parabolic  fpacc, 
extending  downwards  betwixt  the  double  mem- 
brane of  the  larynx,  with  its  faperior  orifice,  of  an 
elliptic  form,  conftantly  open  into  the  larynx. 

ccxcviii.  Laflly,  all  the  internal  cavity  of  the  la- 
rynx is  lined  with  the  fame  foft,  irritable,  mucous 
membrane,  we  before  deferibed  in  the  windpipe 
(ccxxxix.)  This  membrane  is  moifiened  by  a great 
number  of  glands.  The  uppermofi;  are  fmah,  and 
compofed  of  fimple  glands  (ccviii.)  They  are 
feated  on  the  anterior  convex  part  of  the  epiglottis, 
and  fend  prolongations  through  its  various  perfo- 
rations and  larger  fmufes,  to  its  concave'’  fide, 

which 


VOICE  AND  SPEECH. 


Chap.  IX, 


136 

which  arc  there  contin-ued  into  fimilar  nrm  glands. 
Moreover,  upon  the  anterior  furrowed  furface  of 
the  arytenoid  cartilages  (ccxciv.)  there  is  on  each 
lide  a gland,  of  a loofe  conglomerate  fabric,  refem- 
bling  much  a gnomon,  compofed  of  round  acini, 
doubtlefs  mucous,  of  which  a loofe  portion  defcends 
on  each  fide  as  far  as  the  annular  cartilafxe.  In 
the  ventricles,  there  are  numerous  m.ucous  finufes. 
Laftly,  all  the  internal  furface  of  the  larynx  is  full  of 
large  mucous  pores.  All  thefe  glands  fecrete  a thin 
and  watery,  but  at  the  lam.e  time,  \dfcid  mucus. 

ccxcix.  Has  the  thyroid  gland  any  lim.ilar  ufe  ? 
It  is  of  the  conglomerate  kind,  but  foft,  the  cover- 
ings of  the  lobules  being  much  more  tender  than  in 
the  falival  glands,  it  is  very  large,  is  anteriorly  feat- 
ed  upon  the  thyroid  and  cricoid  cartilages  and 
windpipe,  lurrounding  vvith  lateral  produclions  the 
hides  of  the  thyroid,  is  joined  to  its  companion  by 
an  iilhmus,  which  is  narrow  and  emarginated  be- 
low ; and  by  a middle  very  thin  procels  it  afcends 
on  the  forepart,  almoil  to  the  os  hyoides.  This  gland 
is  fuU  of  a ferous,  yellowiCi,  and  fomewhat  vifcid 
humour  : Does  it  difcharge  this  fluid  into  the  wind- 
pipe,  or  into  the  cefophagus  ? Into  neither  are  duels 
certainly  knov/n  to  open.  Does  it  retain  its  fluid 
entirely,  and  afterwards  reftore  it  to  the  veins,  like 
the  thymus,  which  is  analogous  in  its  ftrucnire  ? Is 
it  a conglobate  gland  ? That  the  ufe  of  this  gland  is 
very  coniidcrablc,  appears  from  the  remarkable  fize 
of  the  arteries  which  it  receives  from  the  carotids, 
and  of  its  inferior  ones  from  the  fubclavians.  The 
veins  return  into  the  jugulars  and  fubclavians.  It 
has  a peculiar  mufcle,  not  however  conflant,  arifing 
from  the  maruin  of  the  os  hyoides,  and  fometimes 
from  the  low'Cr  edge  of  the  thyroid  cartilage  to- 
wards the  left,  which  defcends  without  a fellow, 
and  fpreads  its  tendinous  fibres  over  the  gland, 
upon  which  alfo  the  fccrnchycidei  and  fterno.thy- 
loiuci  piufcles  arc  incumbent, 


ccc, 


Chap.  IX. 


VOICE  Aim  SPEECH. 


137 

ccc.  The  whole  larynx  is  fufpended  from  the  os 
hyoides,  both  by  ligaments  inferted  into  the  fupe- 
fior  horns  of  the  thyroid  cartilage,  and  by  the 
middle  of  its  balls,  united  to  the  junction  of  the 
plates,  conftituting  that  cartilage.  The  larynx,  and 
os  hyoides  connefted  with  it,  may  be  raifed  con- 
liderably,  even  half  an  inch  above  its  mean  alti- 
tude. This  is  performed  by  the  biventer  mufcles, 
together  v/ith  the  geniohyoidei,  geniogloffi,  llylo- 
glolli,  ftylohyoidei,  ftylopharyngei,  thyropalatini, 
hyothyroidei ; either  conjunftly  or  partially.  Dur- 
ing its  elevation,  the  glottis  is  rendered  narrower, 
and  the  ligaments  before  mentioned  (ccxcv.)  ap- 
proach nearer  together.  Thus,  by  the  affiilance  of 
the  ad:ion  of  the  arytenoid  mufcles,  both  oblique  and 
tranfverfe,  the  glottis  may  be  accurately  clofed,  fo 
as  to  relift  with  and  incredible  force  the  preliure  of 
the  v/hole  atmofphere. 

ccci.  The  whole  larynx  may  aifo  be  deprelTed 
about  half  an  inch  beneath  its  ordinary  lituation, 
by  the  fternohycidei,  fternothyroidei,  and  coraco- 
hyoidei,  as  they  are  called  ; and,  when  thefe  are 
in  action,  by  the  anterior  and  pofterior  cricothyroi- 
dei.  By  this  motion  the  arytenoid  cartilages  re- 
move from  each  other,  and  the  glottis  becomes 
wider,  v/hich  is  alfo  drawn  open  by  the  mufcles 
laterally  inferted  into  the  aiytenoid  cartilages,  and 
by  the  cricoarytenoidei  poftici  and  laterales,  and 
thyroarytenoidei  ; thefe  alfo,  by  refting  upon  the 
ventricles  of  tlie  larynx  (ccxcvn.)  are  capable  of 
compreffing  them.  The  particular  cartilages  which 
form  the  larynx,  can  fcarcely  be  mioved  feparately. 

cccii.  From  the  larynx  the  air  comes  into  the 
mouth  and  noftrils.  By  the  m.outh,  we  here  mean 
that  large  and  irregularly  fliaped  cavity,  fituated 
between  the  foft  and  hard  palates,  both  concave  in 
the  middle,,  and  the  mufcles  lying  under  them,  and 
the  lower  jaw.  The  noftrils  afcend  forwards  above 


VOICE  AND  SPEECH. 


Chap.  IX. 


135 

the  foft  palate  ; they  are  two  broad  cavities,  in- 
cluded between  the  feptum  medium,  and  the  oiTa 
cavernofa,  and  fome  other  parts.  They  are  every 
where  bony  and  cartilaginous. 

ccGiii.  The  tongue  lies  in  the  middle  of  the 
mouth  ; it  is  a broad  piece  of  flelli  eafily  change- 
able into  any  kind  of  figure,  and  readily  moved 
without  delay  to  any  part  of  the  mouth  ; by  its  own 
fielhy  fibres,  and  by  the  mufclcs  attached  either  to 
itfelf  or  to  the  os  hyoides,  which  is  joined  to  it  by 
many  flelhy  fibres  and  membranes,  it  may  with 
great  facility  be  made  to  affume  any  pofition  or 
figure.  It  is  drawn  forwards  by  the  genioglolTi  and 
geniohyoidei  mufcles  ; backwards  by  the  fiyloglofii, 
fiylohyoidei,  ceratogiofii,  bafiogloffi,  chondroglofii, 
and  biventer  ; downwards,  by  tlie  fiernoliyoidei, 
and  ceratohyoidei ; and  upwards,  by  the  ityloglofli, 
fiylohyoidei,  by  the  biventers,  and  likewife  by  the 
mylohyoidei. 

ccciv.  So  much  for  the  anatomy.  It  remains 
that  we  demon  (Irate  what  efiecds  are  produced  by 
air,  when  expelled,  during  exfpiration,  by  the  pow- 
ers above  defcribed  (cclxix.  cclxx.)  from  the 
lungs  through  the  windpipe  into  the  larynx,  and 
from  thence  forced  through  the  glottis  into  the 
mouth  varioully  configured.  Thefe  effects  are, 
voice,  fpeedr,  and  finging.  Sound  only  is  produ- 
ced when  the  air  is  expelled  with  fo  great  a veloci- 
ty through  the  contracted  glottis,  that  it  impinges 
on  the  ligaments  of  the  glottis,  and  thus  produces 
in  the  larynx  that  tremor,  which,  being  vibratory 
on  account  of  its  elafticity,  it  continues  and  in- 
creafes.  Therefore,  from  the  united  vibrations  of 
the  ligaments  (ccxcv.)  and  of  the  cartilages  of  the 
larynx,  a found  is  produced,  vrhich  we  call  tlie 
voice,  peculiar  in  every  clafs  of  animals,  and  wliidi 
depends  entirely  on  the  larynx  and  glottis.  When 
there  are  no  vibrations,  a wliifper  is-  produced. 

ccev. 


Chap.  IX. 


VOICE  AND  SPEECH. 


139 

cccv.  The  ftrength  of  the  voice  depends  upon  the 
quantity  of  air  exfpired,  and  the  narrownefs  of  the 
glottis  ; and,  therefore,  upon  capacious  lungs  ealily 
dilatable,  an  ample,  cartilaginous  and  elaftic  larynx 
and  windpipe,  the  free  refonance  of  the  noftrils, 
and  a powerful  exfpiration.  But  the  acutenefs  or 
gravity  of  the  tones,  we  obferve  to  arife  from  va- 
rious caufcs.  The  former  proceeds  partly  from  the 
narrownefs,  and  partly  from  the  tenlion  of  the 
glottis,  and  the  latter  from  its  relaxation  and  dila- 
tation. For  hence,  the  air,  in  a given  time,  im- 
pinges upon  the  ligaments  of  the  contrafted  glot- 
tis with  more  numerous  undulations,  and  caufes 
more  frequent  vibrations  ; but  when  the  glottis 
is  dilated,  the  contrary  of  all  this  follows.  And 
from  the  greater  tenlion  of  the  ligaments,  the  tre- 
mors in  like  manner  become  more  numerous  from 
the  fame  ftroke.  Therefore,  to  produce  an  acute 
found,  the  whole  larynx  is  drawn  upwards  and 
forwards  ; and  with  greater  force  as  the  vo;ce  is 
required  to  be  iharper,  infomuch  that  the  head  it- 
felf  is  fometimes  inclined  backwards,  that  the 
mufcles  elevating  the  larynx  may  exert  their  full 
powers.  The  truth  of  this  is  conjlrmed  by  experi- 
ment, for  by  applying  the  fingers  to  the  larynx 
when  acute  founds  are  emitted,  the  elevation  of  the 
larynx,  which  is  about  half  an  inch  for  the  octave, 
is  ealily  felt  : and  by  comparative  anatomy,  which 
demonllrates  the  glottis  to  be  very  narrow  and  car- 
tilaginous in  finging  birds,  and  wide  in  hoarfe  ani- 
mals, and  fuch  as  are  low  or  mute.  This  is  alfo 
illuftrated  by  whiffling,  where  the  llrarpnefs  of  the 
found  evidently  proceeds  from  the  contraction  of 
the  mouth  : and  by  mufical  inltruments,  in  which 
the  narrownefs  of  the  opening  admitting  the  air, 
and  the  celerity  with  which  it  is  impelled,  are  the 
caufes  of  an  acute  tone. 

cccvi.  Gravity  of  the  voice  is  produced  by  op- 
ppfite  drcumltances,  the  deprellion  of  the  larynx 


VOICE  AND  SPEECH. 


Chap.  IV 


T4®' 

by  the  caufes  (ccci.)  already  defcribed  ; a wide 
glottis  and  a very  ample  larynx.  This  is  proved 
by  the  touch,  which  eaiily  perceives  the  defeent 
o£  the  larynx  in  perfons  hnging,  in  like  manner 
about  half  an  inch  for  every  oclave  ; by  the  great- 
er gravity  of  the  voice  in  males,  and  by  the  loweft 
tones  of  the  voice  degenerating  into  a filent  breath- 
ing. 

cccvii.  Does  every  diverhty  of  tone  proceed 
from  the  length  of  the  ligaments  of  the  glot- 
tis, which  is  augmented  when  the  feutiform  car- 
tilage is  drawn  forwards,  and  the  arytenoid  one's 
backwards  ? Is  it  according  to  this  rule,  that  the 
moil  acute  tones  are  produced,  by  the.  ligaments 
being  rendered  very  tenfe,  and  therefore  vibrating 
with  great  celerity  ? This-  is  afl'erted  by  fonie 
late  anatomifts,  from  experiments,  which  have  been 
alfo  repeated  by^  fome  eminent  men ; they^  have 
obferved,  that,  when  the  chords  or  ligaments  of 
the  glottis  are  tenfe,  the  peculiar  voice  of  every 
kind  of  animal  is  produced  by  blowing  air  into  its 
trachea  ; that  this  voice  was  rendered  more  acute 
by  ftretching  the  ligaments,  and  more  grave  by 
loofening  them  ; that  by  Ihutting  the  whole  liga- 
ment, the  voice  was  fupprelTed  ; by  lliutting  the 
half,  the  voice  was  rendered  an  octave  higher  ; by 
flmtting  a third  part,  a fifth  higher,  See.  Ihcre 
are  not  wanting,  however,  doubts  concerning  this 
new  theory,  arifing  from  the  cartilaginous  and 
bony,  and  confequently  immoveable  and  inexten- 
iibie,  glottis  of  birds  ^ from  the  certain  production 
of  more  acute  founds,  ip  whiftling,  from  the  mere 
contraction  of  the  lips  ; from  the  etmmple  of  wo- 
men, in  which  the  larynx  is  fofter,  but  the  voice 
more  acute,  than  in  men  ; from  experiments  which 
lliow,  that  more  acute  founds  are  produced  by 
bringing  the  ligaments  of  the  glottis  nearer  into  con- 
tacc  with  each  other  ; and  from  the  total  abfence  of 
machinery  for  llretching  the  lig-aments,  and  draw- 
ing the  thyroid  cartilage  forwards  from  the  annular 

one. 


Chap.  IX. 


VOICE  AND  SPEECH. 


44* 


one.  But  fince  it  appears  from  experiments,  that 
the  tenfion  of  the  ligaments  fufiices  for  producing 
acute  founds,  without  the  contraction  of  the  glottis, 
it  is  probable  that  difference  of  tenfion  in  the  glot- 
tis contributes  more  than  a difference  of  its  diame- 
ter to  the  diverfity  of  voice. 

cccvm.  Singing,  is  when  the  voice,  modulated 
through  various  degTees  of  acutenefs  and  gravity, 
is  expelled  through  the  lar^mx,  while  vibrating  and 
fufpended  between  contrary  powers,  which  chiefiy 
diftingnifhes  it  from  fpeech.  It  is  a laborious  addon, 
on  account  of  the  perpetual  a<ffion  of  the  mufcles 
poifing  the  larynx ; and  it  increafes  the  animal 
heat,  becaufe  acute  tones  require  a contracted  glot- 
tis, vchich  retards  the  exfpiration,  and  at  the  fame 
time  a great  deal  of  air  to  give  them  ffrength 
(cccv.)  and,  therefore,  deep  infpirations  are  necef- 
Hry.  it  tends  very  much  to  dry  the  windpipe, 
from  the  accelerated  paffage  of  the  air  ; and  ren- 
ders a ^eat  deal  of  mucus  neceffary,  which  is  the 
reafon  why  there  are  fuch  numbers  of  mucous  re- 
ceptacles in  the  larjmx,  amongft  which  I very  much 
fufpedt  the  ventricles  before  defcribed  (ccxcvii.} 
ought  to  be  numbered. 

cccix.  Speech  is  performed  when  the  larynx  is 
at  reft,  in  tones  differing  but  little  in  acutenefs  and 
gravity : by  varioully  modifying  the  voice  by  the 
organs  of  the  mouth.  Canorous  fpeech  has  both 
valuations  in  the  tone,  and  modifications  of  the 
voice  by  the  organs  of  the  mouth. 

cccx.  All  fpeech  is  reducible  to  the  pronuncia- 
tion of  letters,  which  differ  m various  nations,  ai.— 
though  they  agree  in  the  greateft  number  over  the 
whole  world.  Of  thefe,  fome  are  called  vowels^ 
which  are  expreffed  by  the  mere  emifiioii  of  the 
voice  through  the  mouth,  without  the  application 
of  the  tongue  to  any  part  of  the  mouth.  But  con- 
fonants  are  formed  by  a coliificn  of  the  tongue 
againft  fome  part  of  the  mouth,  lips,  or  teeth.  The 

nature 


142 


BRAIN  AND  NERVES. 


Chap.  X, 


nature  of  our  work  forbids  us  to  be  more  particu- 
lar, and  prevents  us  from  explaining  a moil  inge- 
nious art,  which,  a rare  occurrence  in  phyiics,  has 
fo  clearly  determined  all  the  corporeal  caufes  of 
each  letter,  that,  by  mere  infpeclion  and  touch  of 
the  organs  during  their  pronunciation,  it  has 
taught  fpeech  by  imitation. 


CHAP.  X. 

BRAIN  AND  NERVES. 

cccxi.  ^"I'^HE  remaining  actions  of  the  human 
i body  we  fliall  confider  according  to 
the  order  in  which  they  receive  the  blood.  Of  the 
coronary  arteries  we  fpoke,  when  we  gave  the  hif- 
tory  of  the  heart.  Next  to  thofe,  the  catotids  arife 
from  the  aorta. 

CCCXI  I.  The  aorta,  which  comes  out  from  the  an- 
terior part  of  the  heart  (clvii.)  in  order  to  bend  it- 
felf  towards  the  vertebne  of  the  thorax,  inclines 
backwards,  and  to  the  left,  in  an  angle  that  is  round 
indeed,  but  not  very  large,  forming  a confiderable 
arch.  From  the  convexity  of  this  arch,  three 
branches  arife.  The  firft  afcends  towards  the  right 
fide,  and  is  immediately  fubdivided  into  two  large 
arteries,  of  which  the  lowermoft  proceeds  in  the  di- 
redlion  of  its  trunk,  under  the  denomination  of  the 
fubclavian.  The  other  afcends  along  the  wind- 
pipe to  the  head,  and  is  called  the  right  carotid. 
The  left  carotid  fprings  next  from  the  fame  arch,  a 
little  inclined  to  the  left  fide  ; and  the  third,  which 
is  ftill  more  inclined  to  that  fide,  is  called  the  left 
fubclavian,  and  is  fomewhat  lefs  than  the.  right. 
At  tlie  origins  of  thefe  branches,  the  continuous 
fide  of  the  aorta  is  a little  thicker,  and  projecls  a 
little  to  the  left.  Variations  from  this  courfe  are 
rarely  obferved. 


GCCXIII, 


Chap.  X. 


BRAIN  AI'ID  NERVES. 


243 


cccxiii.  The  carotid  artery,  inclofed  alorigwitii 
the  jugular  vein  and  nerve  of  the  eighth  pair,  in 
copious  and  denfe  cellular  fubftance,  commonly  ar- 
rives at  the  upper  part  of  the  thyroid  cartilage, 
without  fending  off  any  branches.  There  it  divides 
into  two  trunks.  The  anterior,  which  is  called  the 
external  carotid,  is  more  in  the  direction  of  its 
trunk,  and  rather  larger.  It  fends  off  the  thyroidea 
fuperior,  the  tortuous  lingualis,and  then  the  labialis; 
and  from  its  poherior  part,  clofe  by  its  divifion,  the 
pharyngea  afcendens,  which,  behdes  the  pharynx 
and  mufcles  of  the  velum  palati,  fupplies  to  the 
dura  mater,  through  the  foramen  common  to  the 
jugular  vein  and  nerve  of  the  eighth  pair,  a confid- 
erable  branch,  fent  off  at  the  bafis  of  the  os  petrc- 
fum,  near  to  the  foramen  magnum,  and  cuneiform 
procefs  of  the  fphenoid  bone. 

cccxiv.  Then,  from  the  exterior  fide  of  the  ex- 
ternal carotid,  fprings  the  occipital  artery  ; whic^ 
alfo  fends  a branch  to  the  dura  mater,  which  is  d^.-. 
tributed,  at  the  bafis  of  the  cerebellum,  through  a. 
peculiar  foramen  of  the  dura  mater  in  the  angle 
which  the  os  petrofum  forms  by  departing  from  the 
mamillary  procefs ; another  branch  paffes  over  the 
atlas  to  the  dura  mater,  both  under  and  into  the 
fkull ; and  a third  fometimes  goes  through  the  foffa 
jugularis  to  the  dura  mater.  The  next  artery,  the 
auricularis,  goes  to  the  back  part  of  the  ear,  to  the 
membrane  of  the  tympanum,  and  to  the  temples. 

cccxv.  What  remains  of  the  external  carotid  ar- 
tery, afcends  through  the  parotid  gland,  to  which 
having  given  fome  branches,  as  well  as  to  the  face 
and  eyelids,  it  fends  out,  in  the  firft  place,  the  tem- 
poralis, which  is  confiderable.  The  trunk  of  the 
carotid,  being  inclined  behind  the  lower  jaw,  lofes 
itfelf  under  the  denomination  of  maxillaris  interna. 
In  that  place,  it  directly  fends  off  a large  trunk 
to  the  dura  maters  which  paffes  through  a pe- 
culiar opening  of  the  broad  pterygoid  wings,  to 

the 


BRAIN  AND  NERVES. 


Chap.  X* 


144 

the  vicinity  of  the  middle  foITa  of  the  brain ; and  is 
largely  diftributed  upon  the  dura  naater,  in  the  re- 
gion of  the  temples  and  forehead,  as  far  as  the  falci- 
form linns.  Sometimes  this  artery  is  double,  and 
often  fends  a confpicuous  branch  to  the  lachrymal 
gland  of  the  eye.  Moreover,  the  fame  maxillary 
artery  enters  the  upper  part  of  the  noftrils  by  a 
triple  trunk,  where  it  is  fpent,  after  having  given 
off  branches  to  the  teeth  of  the  lower  and  upper 
iaws,  the  infra  orbitalis,  a branch  to  part  of  the 
face  and  eyelids,  and  the  palatine  to  the  bone  of 
the  palate,  with  fmall  twigs  to  the  dura  mater,  both 
through  the  fmaller  pores  of  the  great  wings,  and 
accompanying  the  third  and  fecond  branch  of  the 
fifth  pair  of  nerves,  and  the  dura  mater  filling  up 
the  lower  orbital  fiffure. 

ceexvi.  But  the  other  trunk,  which  is  pofferior, 
and  com.mcnly  called  the  internal  cai'otid  (cccxni.) 
afeends  without  a branch.  This  artery,  having 
firft  made  a remarkable  ferpentine  flexure,  enters 
through  a peculiar  forauien  in  the  os  petrofum, 
where  it  is  lurfounded  with  a vagina  from  the  du- 
ra mater,  like  that  which  comes  out  through  all 
the  openings  of  the  flcull : afcer.ding  upwards,  then 
inclining  forwards,  it  penetrates  into  the  cavity  of 
the  fltull,  and  afeends  tortuoufly  bent  along  the  leila 
equina,  in  the  middle  of  the  blood  of  the  cavernous 
finus,  having  given  fmall  branches  to  the  fifth  pair 
of  nerves,  dura  mater,  and  infundibulum,  with 
one  larger  to  the  eye,  part  of  which  returns  Agatin 
through  a peculiar  hole  into  that  part  of  the  dura 
mater,  which  lies  upon  the  middle  of  the  orbit. 
The  rete  mirabile  is'psculiar  to  fome  anim.als,  and 
does  not  exift  in  man. 

cccxvii.  But  the  trunk  of  this  internal  carotid 
paiTes  over  tiic  anterior  part  of  the  felia  equina  ; 
and  being  incurvated  backwards,  and  received  with- 
in the  arachnoid  membrane,  after  giwng  branches 
to  the  pons  and  crura  of  the  brain,  and  a twig  to 


Chap.  1.  BRAIN  AND  NERVES. 


H5 

the  choroid  plexus,  and  a branch  that  accompanies 
the  optic  nerve,  it  then  divides  into  an  anterior  and 
pofterior  branch.  The  former  being  conjoined 
with  its  fellow  artery  of  the  other  fide  by  a fiiort 
anaftomofis,  is  then  incurvated  backwards  and  up- 
wards, along  the  corpus  callofum,  and  goes  to  the 
middle  and  pollerior  part  of  the  brain,  and  fome- 
times  fends  branches  to  the  falciform  procefs,  and 
at  its  very  origin  to  the  third  ventricle,  the  fornix 
and  thalaini.  The  latter,  being  joined  by  a mode- 
rate anafiomofis  with  a branch  of  the  vertebral  ar- 
tery, unlefs  that  arife  from  the  undivided  trunk  of 
the  carotid,  afterwards  afcends  a long  way  through 
the  foffa  of  Sylvius  to  the  lateral  part  of  the  brain  ; 
and  alfo  fends  branches  to  the  choroid  plexus.  AH 
the  branches  of  the  carotid,  contained  within  the 
Ikull,  have  a thin,  folid,  and  more  brittle  fubftance 
than  the  other  arteries  of  the  body. 

ccc'xviii.  The  vertebral  artery  commonly  arifes 
from  the  fubclavian  of  the  fame  fide,  (though  the 
left  has  been  fometimes  feen  to  fpring  from  the 
trunk  of  the  aorta,)  in  a deep  fituation,  and  without 
giving  branches,  it  enters  the  foramen  in  the  tranf- 
verfe  procefs  of  the  fixth  vertebra  of  the  neck  ; af- 
ter which,  it  afcends  with  alternate  flexures  through 
the  proceffes  of  the  other  vertebrae  of  the  neck ; 
through  each  interval,  it  fends  off  fmall  branches  to 
the  mufcles  of  the  neck,  and  communicates  with 
the  lower  thyroidal : with  other  branches,  fome- 
what  larger  and  pofterior,  it  accompanies  each 
nerve  to  the  pia  mater  of  the  fpinal  marrow  ; and 
by  anterior  branches,  not  fo  numerous,  but  larger, 
it  communicates  in  the  fpinal  marrow  with  its  an- 
terior artery.  Laftly,  having  becom.e  tranfverfe  by 
a fmall  flexure  at  the  fecond  vertel^ra,  and  by  a 
large  one  round  the  procefs  of  the  firft,  having 
there  given  oft'  two  confiderable  branches  to  the 
mufcles  of  the  neck,  and  during  its  palfage  through 
the  foramen  magnum,  having  lent  fmall  ones  to  the 
L dura 


BRAIN  AND  NERVES. 


Chap.  X, 


146 

dura  mater  of  the  foramen  magnum  and  neighbour- 
ing cavity  of  the  cerebeilum,  it  finally  enters  the 
cavity  of  the  ikull  through  that  foramen.  There, 
while  it  afcends  along  the  medulla  oblongata,  the 
right  trunk  gradually  approaching  the  left,  unites 
with  it  at  a very  acute  angle  (a  moil  uncom.mon' 
circumftance)  into  one  artery,  the  bafilary,  which 
being  ftretched  under  the  pons  Varolii,  is  fufpcnded 
in  the  pia  mater.  From  the  vertebral  arteries,  be- 
fore they  are  conjoined,  or  from  their  common 
trunk  juft  formed,  arteries  both  going  to  the  lower 
furface  of  the  cerebeilum,  and  entering  deeply  into' 
the  fourth  ventricle  and  the  internal  fubftance  of 
the  cerebellum,  arife.  Thefe  fend  off  the  fpinal  ar- 
teries. There  are  inftances  where  thefe  arife  from 
the  united  trunk  ; or  from  the  trunk  in  one  fide,  ‘ 
and  from  a branch  in  the  other.  Then  the  bafila- 
ris,  belides  branches  to  the  medulla  oblongata  and 
crura  of  the  brain,  fends  off  other  lower  arteries  of 
the  cerebellum.  Amonoft  thefe  branches  alfo  arifes 

O 

the  artery,  which  accompanies  the  auditory  nerve. 
Finally,  the  bafilaris,  at  the  forepart  of  the  pons, 
divides  on  each  fide  into  two  brandies.  One  of 
thefe  goes  to  the  upper  part  of  the  cerebellum,  to 
the  fourth  ventricle,  to  the  crura  of  the  medulla  of 
the  cerebellum,  the  nates,  teftes,  and  pineal  gland  : 
in  place  of  this,  aifo,  there  are  two  trunks.  The 
other,  the  profunda  cerebri,  is  diffributed  to  the 
pofterior  lobe  of  the  brain,  the  choroid  plexus,  the 
plexus  lying  on  the  pineal  gland,  that  gland  itfelf, 
the  thalami,  corpora  ffriata,  fornix,  and  whole  an- 
terior ventricle. 

cccxix.  Fro;.n  the  foregoing  hiffory  of  the  ar- 
teries belonging  to  the  brain,  it  appears,  tliat  in ' 
every  pulfation  a great  quantity  of  blood  is  fent  to 
this  organ,  equal  to  a fixth  part  or  more  of  the 
whole  blood  in  the  human  body,  and  conveyed  by 
trunks  which  arife  very  near  the  liearf,  and  from 
the  convexity  of  the  aorta.  It  is  therefore  not  im- 
probable. 


BRxlIN  AND  NERVES. 


Chap.  X. 


147 


probable,  that  the  fcroingeft  parts  of  the  blood,  and 
thofe  moll  retentive  of  motion,  goto  the  head.  Is 
not  this  evident  from  the  elFedls  of  mercurials  being 
almoll  confined  to  the  head  ; from  the  fpdden  ac- 
tion of  inebriating'fpirits  upon  the  head  ; from  the 
fpeedy  llupor  excited  by  camphor  ; from  the  face 
being  oftner  affected  by  heat  and  fweat,  than  any 
other  part  of  the  body ; and  from  the  eruption  of 
highly  volatile  miafmata  upon  the  face  ? The  fafe 
lituation  in  which  the  arteries  of  the  head  afcend, 
defends  the  large  and  important  veffels  from  injury. 
The  frequent  reciprocal  inofculati-oiis  of  the  trunks 
going  to  the  head,  as  well  as  of  their  branches,  di- 
minifli  the  danger  of  obftrudion.  Hence,  when 
the  carotids  are  tied,  aninials  neither  die,  nor  feem 
to  be  very  uneafy.  The  conliderable  flexures  of 
the  vertebral  and  carotid  arteries,  ferve  to  mode- 
rate the  impulfe  of  the  blood  coming  to  the  brain, 
flnce  a great  part  of  the  velocity,  which  it  receives 
from  the  heart,  is  thus  fpent  in  changing  the  figure 
of  the  infleftions.  Some  reputable  authors  have 
obferved,  that  the  arteries  are  fomewhat  large!  at 
this  place. 

cccxx.  The  hiftory  of  the  brain  ptoperly  co^'n'- 
mences  with  its  integuments.  A part  fo  tender  and 
fo  neceffary  to  life,  is,  in  the  firft  place,  furrounded 
by  an  offeous  fphere  compofed  of  many  pieces, 
which,  therefore,  admits  of  extenfion,  while  it  ef- 
feflually  refills  external  preffure.  To  every  part 
of  the  internal  furface  of  this  fphere,  a very  llrong 
membrane  adheres,  compofed  of  two  plates  fuffi- 
ciently  dillincl.  It  is  firmly  attached  by  an  infinite 
number  of  fmall  veflels,  even  penetrating  to  the  ex- 
terior parts  of  the  head,  as  by  fo  many  footllalks  ; 
in  a healthy  perfon  it  is  no  where  detached,  but 
adheres  fomewhat  lefs  firmly  to  the  very  fmooth 
bones,  but  with  exceflive  ftrength  to  the  commif- 
fures  of  the  bones  of  the  Ikull,  whicli,  from  their 
figure,  are  called  futures.  In  young  lubjefts,  the 
h 2 adhelion 


BRAIN  AND  NERVES.  Chap.  X, 


145' 

adheilon  of  the  dura  mater  to  the  fkuU  is  fo  great, 
that  the  fibres  to  v/hich  it  fs  connected  are  fepa- 
rated  at  the  fame  time  with  it.  In  adults,  many 
of  the  veiTels  being  effaced,  the  dura  mater  becomes 
lefs  infeparable  ; but  yet  it  cannot  be  detaclred  from 
the  ficull  without  forae  violence.  Hence  thofe 
bloody  drops  which  appear  on  remo'/ing  tlie  cra- 
nium. tience  all  that  has  been  advanced  concern- 
ing the  motion  of  the  dura  mater  is  erroneous.  As 

O ^ ^ 

to  the  motion,  which  has  been  remarked  in  wounds 
by  fome  obfervers,  it  arofe  either  from  the  puffa- 
tion  of  the  arteries,  in  a place  whence  the  refiffancc 
was  removed,  vchile  the  reff  of  the  cranium  afford- 
ed iniuperable  refiftance  to  the  action  of  the  heart, 
or  from  the  turgefcence  of  the  brain.  The  dura 
mater  lias  neither  irritability  nor  fenfibility,  and  is 
dellitute  of  nerves,  though  thofe  going  to  other 
parts  have  been,  by  fome,  uferibed  to  this  mem- 
brane. 

cccxxi.  It  is  the  external  lamina  of  the  dura 
mater,  which  adheres  to  the  bones,  and  ferves 
them  for  a perloffeum.  It  paffes  out  of  all  the 
holes  of  the  Ikuil  along  the  nerves  and  veffels,  and 
coheres  vcitli  the  perioffeum  of  the  head,  vertebrae, 
and,  laftiy,  of  the  whole  body ; from  which  cir- 
cumffance,  the  name  of  mater  given  to  it  by  the 
barbarians,  is  derived.  The  internal  plate  of  the 
dura  mater  is,  in  moft  pai'ts,  continuous  with  the 
former  : but,  in  fome,  it  recedes  a little  from  it,  as 
in  the  great  fphenoidal  wings ; at  the  fides  of  the 
i'ella  equina,  where  a good  deal  of  blood  is  poured 
lietw  ixt  them  ; and  upon  the  fella  equina  itfelf : 
liaviilg  left  tire  external  laiuina,  which  adheres 
hrmly  to  the  bones,  it  defeends  double  to  form  the 
falx,  which  arifes  hrft  from  the  multiform  bone 
behind  the  criihi  galli,  then  from  the  enfta,  after- 
wards from  the  whole  juncture  of  the  two  frontal 
2md  parietal  bones,  and,  lauly,  from  the  middle 
and  back  part  of  the  occipital  bone ; it  becomes 

broader 


Chap.  X. 


BRAIN  AND  NERVES. 


14-9 

■broader  as  it  proceeds  backwards  ; it  is  interpofed 
betwixt  the  heinifpheres  of  the  brain  ; and  hangs 
over  the  corpus  caliofuin,  at  a greater  diftance  in 
the  forepart,  but  very  near  behind,  where  it  ahb  is 
extenuated  to  an  edge.  That  there  are  fhining 
fibres  in  this  part,  difperfed  towards  the  longitudi- 
nal finus,  from  its  junction  with  the  tentorium,  in 
the  lhape  of  palm  branches,  is  certain  •,  but  it  does 
not  therefore  follow,  that  they  have  any  mmfcular 
motion : betwixt  thefe  fibres  frequently  there  is  no 
membrane, "fo  that  they  form  natural  foramina.  The 
falx  is  joined  to  the  middle  of  the  tentorium,  and  is 
continuous  with  it.  In  the  fame  manner,  but  in  a 
different  fituation,  the  fame  lamina  forms  the  fiiort 
falx  of  the  cerebellum,  feparating  its  lobes,  togeth- 
er with  the  ftrong  tentoria,  wltich,  arifiiig  from 
the  cruciform  protuberance  of  the  occiput,  are  in- 
terpofed tranfverfely  betvdxt  the  brain  and  cere- 
bellum, and,  at  lail,  adhering  to  the  petrous  bones 
and  anterior  clinoid  procefi’es,  leave  an  aperture 
nearly  oval  for  the  medulla  oblongata.  Thefe  pro- 
ductions of  the  dura  mater,  prevent  any  part  of  the 
brain  from  preffing  on  the  reft,  in  any  fituation  of 
the  body  j and,  iikewdfe,  one  lobe  from  compref- 
fing  another,  in  concufiions  of  the  brain.  Hence, 
in  the  fwifteft  quadrupeds,  where  the  danger  from 
concuffion  is  greater,  the  bra,in  and  cerebellum  are 
divided  by  a bony  partition. 

cccxxii.  Upon  the  external  furface  of  the  pia 
mater,  not  far  from  the  finus  of  the  falx,  are  placed 
glands,  feated  in  the  reticular  texture  of  the  dura 
mater,  which  partly  are  inclined  towards  the  finus 
and  its  cavity,  fo  that  fome  of  them  are  contiguous 
to  the  cavity  of  the  finus,  while  others  are  fo  plac- 
ed at  the  infertion  of  the  larsfe  veins  into  the  pia 

X 

mater,  that,  together  with  the  former  jufi  mention- 
ed, they  make  up  a continued  ferics  ; thefe  are 
fometimes  foft,  oval,  and  white,  fornetimes  red,  and 
hal'd,  like  warts.  They  have  alfo  been  noticed  in 


Chap.  X, 


150  BRAIN  AND  NERVES, 

the  tentorium  cerebelli.  But  the  vapou-r,  which 
exhales  from  the  furface  of  tbe  pia  mater,  is  not 
fecreted  by  thefe  glands ; for  every  v/here,  even 
where  there  are  none  of  thofe  glands,  as.  in  the 
ventricles,  a copious  vapour  tranfpires  from  thf 
ultimate  arteries,  as  is  proved  by  injections  of  wa- 
ter or  iise,  which  exude  from  every  part  of  the 
furface  of  the  pia  mater. 

cccxxiii.  The  next  covering  of  the  brain,  m.uch 
clofer  to  it,  and  exprelhng  its  figure,  as  the  former 
does  that  of  the  cavity  of  the  fkull,  has  been  de- 
nominated, from  its  tenuity,  arachnoid.  Pellucid 
as  water,  very  thin,  and  as  far  as  its  thinnefs  petr 
mils,  firm,  it  completely  envelopes  the  brain,  paff, 
ing  over  its  larger  and  fmaller  furrows,  and  in- 
clofing  the  larger  vefTels,  fo  that  they  lie  between 
the  arachnoides  and  pia  mater.  It  is  not  a lamina  of 
the  pia  mater,  from  which  it  differs  in  fituation, 
in  being  connecled  with  it  by  cellular  fabflance, 
and  in  the  exarnple  of  the  fpinal  marrow,  although 
it  is  refolved  into  a cehular  nature  between  the 
hemifpheres  of  the  brain. 

cccxxrv.  The  third  covering  of  the  brain,  is 
the  pia  mater,  or  foft  membrane  of  the  brain. 
This  immediately  inr  efts  the  whole  furface  of  the 
brain  and  fpinal  marroAV  on  all  fides,  is  tender,  and 
compofed  of  a vaft  number  of  fniall  veftels  joined 
together, by  cellular  texture:  but  thefe  veiiels  it 
fends  into  the  brain  in  a regular  order,  like  little 
roots.  It  defeends  into  all  the  finuofities,  and  in- 
fmuates  itfelf  into  the  fiffures  of  the  brain,  cere- 
bellum, and  fpinal  marrow,  and  is  the  bond  by 
which  the  lobules  of  the  brain  are  joined  together, 
being  pollefled  of  confiderable  firmnefs  in  propor- 
tion to  its  tenuity.^  Being  received  into  the  caw- 
ties  of  the  brain,  it  changes  its  fabric,  and  becomes 
foft  and  aim  oft  of  a micdullary  comlftence,  efpe- 
cially  \\  hen  the  fubjeci  is  dilTcc^ed  fame  time  after 
death,  although  the  veftels  itiil  point  it  ou^ 

ccex;j;v, 


Chap.  X.  BRAIN  AND  NERVES.  151 

cccxxv.  The  veins  in  the  brain  are  not  con- 
hrucled  as  in  other  parts  of  the  body.  For  neither 
have  they  any  valves,  nor  do  they  accompany  the 
arteries,  nor  have  their  trunks  the  common  ftruc- 
ture  which  prevails  in  other  veins.  Therefore, 
from  the  innermoft  cavities  of  the  -brain,  the  veins 
which  reft  upon  the  ridges  of  the  ftriated  bodies, 
the  veins  of  the  choroid  plexus,  of  the  lucid  fep- 
tum  and  of  the  anterior  ventricles,  are  colleffed 
into  trunks,  which  at  laft  meet  in  one  great  vein, 
or  often  two,  which,  being  accompanied  with  m.any 
fmall  arteries  of  the  choroid  plexus,  defcends  back- 
wards to  the  partition  of  the  brain  and  cerebellum. 
In  that  place,  it  receives  veins  ariftng  from  the 
pofterior  and  lower  part  of  the  brain,  and  lome  of 
the  cerebellum,  and  meets  with  a fmus  or  vein,  in- 
cluded in  a reduplication  of  the  inner  lamina  of 
the  dura  mater,  and  being  changed  into  this  finus, 
it  generally  defcends  into  the  lefs  tranfverfe  fmus, 
moft  frequently  of  the  left  fide,  though  fometimes 
dividing,  it  fends  a branch  to  each  fide.  This  is 
called  the  fourth  ftnus. 

cccxxvi.  The  fuperior  and  fuperficial  veins  of 
the  brain  are  large,  and  fpread  in  the  windings 
with  which  the  brain  on  all  fides  abounds.  Into 
thofe  veins,  over  the  whole  ftirface  of  the  brain, 
are  infer  ted  fome  veins  of  the  dura  mater  ; while 
others  of  them  enter  by  peculiar  orifices  into  the 
falciform  finus.  Then  the  veins  being  gradually 
collefled  into  trunks,  proceed,  the  greateft  number 
of  them  forwards,  a few  either  directly,  or  back- 
wards, and  thefe  moft  efpecially  from  the  forepart, 
.and  infert  themfelves,  vcith  their  terminations  ob- 
liquely truncated,  into  the  long  falciform  finus 
which  is  form.ed  by  the  internal  lamina  of  the  dura 
mater,  from  the  right  and  left  fide  miceting  togeth- 
er below  in  the  upper  edge  of  the  falx.  There- 
fore it  is  of  a triangular  figure,  convex  in  its  upper 
fide.  It  begins  with  a ilender  origin  at  the  foramen 

caecum. 


152  BRAIN  AND  NERVES.  Cka?.  X. 

cfficum,  which  lies  before  the  criRa  galli  ; it  af- 
cends  and  follows  the  courfe  of  the  falx  ; where 
that  joins  the  tentcrinm,  being  generally  inclined 
to  the  right,  it  takes  the  name  of  the  right  tranf- 
verfe  finus,  and  goes  by  a peculiar  channel  impreff- 
ed  in  the  occipital  and  temporal  bones,  firft  tranf- 
verfely,  then  incurvated,  to  the  foramen  jugulare, 
where,  becoming  very  large,  it  receives  the  inferior 
petrous  and  the  occipital  finufes,  and  empties  itfelf 
into  the  jugular  vein.  But  the  left  tranfverfe  iinus, 
refembling  the  former,  and  alfo  leading  to  the  ju- 
gular vein,  is  rather  inferred  into  its  riglit  lide, 
than  continued  as  its  trunk.  Into  it  the  fourth 
finus  (cccxxv.)  and  the  occipital  one,  ufoaily  infert 
tliemfclvcs.  But  there  are  fome  infcances  of  a re- 
verfe  arrangement,  lb  thc^t  the  longitudinal  fmus 
terminates  in  the  left  tranfverfe  fmus  ; and  then 
the  right  tranfverfe  linns  receives  the  fourth  and 
the  occipital  one.  At  other  times  it  is  equally  di- 
vided into  tveo  tranfoerfe  trunks  ; and  fometimes 
a middle  linns  joins  the  tranfverfe  ones.  There 
even  have  been  found  two  fimilar  fmufes  parallel  to 
each  other. 

cccx:cvii.  Irregularly  parallel  with  the  lower  and 
tl'dckcr  margin  of  the  falx,  runs  a llendcr  and 
rounder  hnus,  more  refembling  a vein  ; it  receives 
veins  from  the  folx  itfelf,  Vvdaich  alfo  communicate 
with  the  npper  fmus  ; and  from  the  adjacent  hem- 
ifphcres  cf  the  brain,  and  from  the  corpus  callo- 
fum.  Vt^hcre  the  falx  joins  with  the  forepart  of 
the  tentorium,  it  is  inferted  into  the  fourth  finus. 

cccxxviii.  The  lower  veins  of  the  brain,  which 
lie  next  to  the  bafis  of  the  Ikull,  are  variouliy  in- 
ferled.  The  anterior  veins  coming  from  tlie  folia 
Sylvii,  collected  into  fome  trunks,  are  inferted  into 
the  cavernoa-s.  fmus,  or  that  triangular  interval,  be- 
tween the  external  and  internal  plates  of  the  dura 
mater,  which  is  at  the  fide  of  the  fella  equina. 

Other 


BRAm  AND  NERVES. 


Chap.  X. 


5 53 


OLiier  veins,  from  the  pons  itfelf,  lead  into  the  up- 
per finus  petrofus.  Other  pofterior  veins,  which 
come  from  the  pofterior  lobes  of  the  brain,  are  in- 
ferted  in  great  numbers  into  the  tranfverfe  linufes 
in  the  tentorium. 

cccxjiix.  The  upper  veins  of  the  cerebellum, 
meeting  together  in  large  trunks,  partly  terminate 
in  the  fourth  finus,  and  partly  in  the  tranfverfe 
finufcs.  The  lower  veins,  from  the  cerebellum  and 
meduUa  oblongata,  infert  themfelves  into  the  upper 
finus  petrofus  ; and  fome  of  thefe  alfo  into  the 
tranfverfe  finus  very  near  the  place  where  it  goes 
out. 

cccxxx.  There  are  many  finufes,  befides  thofe 
now  mentioned.  The  moft  anterior  of  them,  which 
commonly  has  a circular  appearance,  furrounds  the 
pituitary  gland,  and  betrveen  the  clinoid  procefies, 
communicates  witfi  the  cavernous  finufes  ; and  be- 
tw’een  thefe  proceffes  and  the  carotid,  with  the  low- 
er petrous  finufes,  and  laitly,  by  the  way  of  the 
fixth  pair,  with  the  upper  petrous  finufes  behind 
the  fifth  nerve.  There  are  fome  inftances  where 
this  finus  receives  the  ophthalmic  vein  ; and  fome- 
times  the  tranfverfe,  joining  to  the  cavernous  finus, 
fupphes  the  place  of  this  circular  finus,  or  elfe  co> 
exilis  with  it. 

cccxxxi.  The  upper  petrous  finus  runs  back- 
wards in  a groove  of  the  os  petrofum.  It  arifes 
from  the  anterior  extremity  of  the  falcus  of  the  os 
petrofum,  where  it  communicates  v/ith  the  caver- 
nous finus  ; it  receives  veins  of  the  dura  mater 
which  are  inferted  into  it,  and  fometimes  ante- 
rior veins  of  the  brain  itfeif,  mentioned  before 
(cccxxviii.)  and  is  inferted  into  the  angle  of  the 
tranfverfe  finus,  where  it  begins  to  be  bent,  and 
fometim.es  into  the  inferior  petrous  finus.  Another 
vein,  paffing  along  the  top  of  the  os  petrofum,  is  in 
like  manner  inferted  into  the  angle  of  the  tranfverfe 
finus.  The  io'wer  finus  petrofus,  which  is  fiiorter 


BRAm  AOT  NERVES. 


Chap.  X, 


554 

and  larger,  goes  round  the  root  of  the  bone  of  this 
name,  and  communicates  with  is  fellow  behind  the 
clinoid  procefs ; after  twice  communicating  with 
the  cavernous  iinus,  and  with  the  upper  linus,  un- 
der the  nerve  of  the  fifth  pair,  it  is  finally  inferted 
into  the  jugular  foifa ; it  alfo  receha^s  fome  veins 
of  the  dura  mater  from  the  region  of  the  verte- 
brae. To  the  fame  outlet  alfo,  the  nofterior  occi- 
pital  finus  on  each  fide  leads.  Thefe  are  pretty 
large,  go  round  the  margin  of  the  foramen  mag- 
num, till,  arriving  at  the  falx  of  the  cerebellum, 
{cccxxi.)  they  are  fooner  or  later  inferted,  gener- 
ally after  being  conjoined  into  the  fourth  finus, 
and  with  that  into  the  left  tranfverfe  one,  or  imme- 
diately into  this  finus  itfelf,  or  lafdy,  by  a divided 
extremity  into  each  of  the  tranfverfe  finufes.  It  re- 
ceives the  lower  and  pofterior  veins  of  the  dura 
mater,  and  feune  from  the  vertebrae. 

cccxxxii.  The  anterior  occipital  finus,  irregular 
and  multiform,  partly  tranfverfe,  and  partly  de- 
feending  to  the  great  foramen,  is  united  in  various 
ways  with  the  lower  petrous  finufes  ; from  whence 
branches  either  accompanying  the  nerves  of  the 
ninth  pair,  or  pafiing  through  a peculiar  foramen, 
communicate  with  the  external  vertebral  vein  ; 
while  otlier  branches,  going  downwards,  open  into 
the  venous  circles  of  the  fpinal  marrow.  But  the 
cavernous  finus  of  the  dura  mater,  (cccxxv.)  which 
is  furrounded  with  a good  deal  of  cellular  fubftance, 
befides  the  finufes  (cccxxix.  cccxxx.)  and  large 
veins  already  deferibed,  alfo  receives  the  ophthalmic 
and  principal  vein  of  the  dura  mater ; it  likevnfe 
tranfmits  peculiar  veins,  accompanying  the  firft,  and 
fecond,  and  third  branches  of  the  fifth  pair,  the  prin- 
cipal artery  of  the  dura  mater,  (ceexvi.)  and  the  in- 
ternal carotid,  (ceexvi.)  and  alfo  through  a foramen 
in  the  great  wing,  which  is  not  conftant  ; it  fends 
branches  which  inofculate  evith  veins  on  the  outfide 
of  the  Ikuil  belonging  to  the  jugulars,  and  efpeciaily 
with  the  large  pterygoid  plexus  of  the  nafal  veins. 


Chap.  X. 


BRAIN  AND  NERVES. 


155 

In  the  fame  manner,  the  veins  of  the  pericranium 
pafs  through  foramina  in  the  parietal  bones  into  the 
longitudinal  fmus,  the  occipital  veins  through  the 
maftoid  hole  into  the  tranfverfe  fmus,  and  the  ex- 
ternal vertebral  veins  through  the  anterior  canal  of 
the  occipital  bone,  into  the  folfa  jugularis ; and 
others  from  the  anterior  occipital  veins  accompany 
the  nerve  of  the  ninth  pair.  Thus  there  are  an  in- 
finite number  of  ways  open  to  the  blood,  by  which 
it  may  efcape  from  the  linufes,  wherein  it  is  often 
collected  in  too  great  quantity,  in  various  directions, 
according  to  the  laxity  or  declivity  of  the  part. 
Hence  no  violent  fymptoms  follow  upon  tying  a 
vein,  hov/ever  large,  or  even  both  the  jugulars. 

cccxxxiii.  The  quantity  of  blood  which  goes  to 
the  brain,  the  great  impulfe  with  which  it  is  fent 
into  the  carotid  arteries,  (cccxix.)  the  immunity  of 
a part  defended  by  bones  from  every  kind  of  pref- 
fure ; the  flow  motion  of  the  blood  through  the 
abdominal  vifcera  and  lower  extremities  5 the  per- 
petual exerciie  of  the  brain  and  fenfes,  which  de- 
termines an  influx  of  blood  to  thefe  parts,  and 
other  circumftances,  caufe  the  head  to  be  furprif- 
ingly  filled  v/ith  blood,  immediately  on  any  increafe 
of  the  circulation.  Hence  the  rednefs  of  the  face, 
the  turgefcen.ee  of  the  eyes,  the  fparkling,  the  head- 
ach,  the  throbbing,  the  haemorrhages  from  the  nofe, 
which  are  fo  frequently  produced  by  violent  exer- 
cife.  Therefore,  it  is  evidgnt,  that,  if  the  veins  in. 
the  brain  were  thin  and  round,  the  imminent  dan- 
ger of  rupture  and  apoplexy,  even  now  frequent, 
could  not  poflibly  be  avoided.  On  this  account, 
to  the  veins  which  carry  out  the  blood  from  the 
brain,  nature  has  given  another  form  more  eafily 
dilatable,  becaule  it  makes  an  unequal  refiflance  5 
and  another  texmre,  of  great  firmnefs,  and  more 
difficultly  ruptured,  efpeciaUy  in  the  large  finufes, 
which  perform  the  office  of  trunks  ; for  the  fmall- 
er  finufes  are  either  rounder,  half  cylindrical,  or 


BRAIN  AND  NERVES. 


Chap.  X. 


ts& 

of  an  irregular  figjire.  Within,  nature  has  furnifhed 
thehnufes  with  crofs  braces,  formed  of  ftrong  mem- 
brane, palling  from  the  right  fide  of  the  bottom  of 
the  finus-to  the  left,  w^hich,  in  excefilve  difientions, 
ftrengthen  the  acute  angle  wdiich  is  moft  diftended, 
and  fecure  it  from  rupture.  She  has  likewife,  in 
thefe  veins,  provided  numberlcfs  inofculations,  both 
mutually  amongft  themfelves,  and  with  the  external 
veflels  of  the  head,  and  with  thoie  of  the  fpinal 
marrow,  that  they  m^ay,  wfith  greater  facility,  dif- 
cliarge  their  fuperabundant  blood,  (cccxxxii.) 

cccxxxiv.  Is  arterial  blood  aJfo  poured  into  the 
finuics  of  the  brain  ? Do  they  pulfate,  by  being  ex- 
cited by  that  blood  ? It  is  alloveed,  that  they  have 
no  pulfiition ; becaufe  the  dura  mater  every  way 
adheres  to  the  fnui],  and  moft  firmly  in  the  regions 
of  the  finufes.  They  certainly  receive  liquors  in- 
jccfed  by  tlie  aiteries.  Whether  are  thcfc  exhaled 
through  the  fmalL  vcfiels,  or  do  they,  in  the  find 
place,  circulate  through  the  veins  ? The  latter  opin- 
ion is  much  more  probable. 

cccxxxv.  Ail  the  blood  of  the  brain  is  finally 
conveyed  into  the  jugular  veins,  which  are  very 
dilatable,  and  for  that  reafon  protected  by  valves, 
againfe  the  regurgitation  of  blood  from  the  auricle, 
and  furrounded  with  a great  quantity  of  cellular 
fubfiance.  For  the  blood,  which  comes  from  tlic 
head  to  the  vertebral  veins,  is  very  inconfiderable. 
The  jugulars,  fo  direffly  correfpond  with  each  of 
the  principal  branches  of  the  vena  cava  fuperior, 
tha,t  they  bring  back  the  blood  to  the  heart  in  the 
fliortefi;  way,  and  that  the  right  one  proceeds  in  a 
ftraight  line  from  the  right  auricle.  They  feparate 
nearly  as  the  arteries,  into  a facial  and  cerebral 
branch. 

ccacxxvi.  The  external  jugular  is  a cutaneous 
vein  of  the  neck,  which  gives  off  the  temporal  one  : 
it  is  united  by  a broad  anafiomofis  with  the  internal 
jugular  at  the  bans  of  the  loveer  jaw } and  fends  a 

biTtUcii 


Chap.  X. 


BRAIN  AND  NERVES. 


257 

branch  through  the  os  mamillare  into  the  tranf- 
X’^erfe  finus.  The  internal  vertebral  empties  itfelf 
through  the  tranfverfe  proceiles  of  the  neck  into 
the  tranfverfe  finus,  -when  the  canal  belonging  to  it 
is  open. 

cccxxxvii.  The  firtufes  of  the  fpinal  marrow, 
which  are  two  in  number,  and  lateral,  run  along 
its  whole  length,  are  joined  at  each  vertebra  by  a 
femicircular  arch,  and  are  finally  united  with  the 
jugular  and  occipital  finufes ; they  fend  branches, 
however,  to  the  fpinal  marrow,  communicatingwith, 
the  anterior  and  pofterior  fpinal  veins. 

cccxxxviii.  In  confequencc  of  the  innumerable 
anaftomofes  of  the  veins,  tlie  blood  returns  with  the 
greatefi;  facility  from  the  head,  of  which  the  reple- 
tion is  attended  with  much  danger.  During  infpi- 
ration,  the  brain  is  alfo  more  eafily  evacuated,  and 
fubfides  when  the  fkull  is  opened ; during  exfpira- 
tion,  on  the  contrary,  it  fwells.  Hence,  blowing 
the  nofe,  fneezing,  and  coughing,  are  dangerous  to 
thofe  whofe  brain  is  turgid  with  retained  blood. 

cccxxxix.  Have  lymphatic  vefl'els  been  feen  with 
certainty  in  the  brain  ? They  have  been  defcribed 
in  the  large  choroidal  plexus,  amongil  the  fibres  of 
the  olfaHory  nerve,  and  in  the  pia  mater.  For  my 
ov/n  part,  I have  never  feen  them,  and  it  is  prob- 
able that  there  are  none,  fince  there  are  no  conglo- 
bate glands  in  the  brain,  which  are  always  found 
near  thefe  veffels.  As  for  the  various  accounts 
which  are  given  of  the  pituitary  gland,  of  the  in- 
fundibulum, and  of  the  ducts  which  lead  from 
thence  into  the  veins  of  the  head,  abforbine'  water 
from  the  ventricles,  they  are  not  fupported  by  any 
anatomdcal  demonftration  : which  makes  it  proba- 
ble, that  the  vapour,  which  is  fecreted  into  the  ven- 
tricles of  a healthy  perfon,  is,  in  like  proportion, 
abforbed  again  by  the  inhaling  veins  ; and  that  if 
there  be  any  excels,  it  defcends  through  the  bottom 
of  the  ventricles  to  the  bafis  of  the  fkull,  and  into 

the 


BRAIN  AND  NERVES. 


Chap.  N. 


'158 

' the  loofe  cavity  of  the  fpinal  marrow.  That  this 
is  the  cafe,  appears  from  paliies,  which  cnfue  after 
apoplexies  ; and  from  the  v/atery  tumours  in  the 
lower  part  of  the  fpinal  marrow,  in  hydrocephalic 
patients. 

cccxL.  It  now  remains  for  us  to  fpeak  of  the  en- 
cephalon itfelf.  There  are  feveral  parts  included 
under  this  general  denomination.  By  the  brain, 
properly  fo  called,  v/e  underhand  the  upper  part  of 
that  viicus,  which  is  contained  in  the  Ikull,  and 
which  alone  occupies  its  anterior  portion  ; but  be- 
hind, it  lies  above  another  part,  called  the  cerebel- 
lum, which  is  htuated  in  the  pofterior  and  lower 
cavity  of  the  occipital  bone,  under  the  tentorium. 
Its  lower,  middle,  and  white  portion,  lying  under 
the  brain,  and  before  the  cerebellum,  is  in  part  call- 
ed the  pons,  and  in  part  the  medulla  oblongata. 

CCCXL  I.  The  figure  of  the  brain  refembles  that 
of  half  an  egg,  which  is  deeply  divided  longitudi- 
nally, not  through  the  whole,  but  through  more 
than  the  half  of  its  length,  into  hemifpheres,  re- 
fcmbllng  the  quarters  of  an  egg.  Both  the  upper 
and  lower  furfaces  in  man,  are  full  of  convolutions, 
v/hich,  with  alternate  round  angles,  pretty  deeply 
divide  the  brain  into  undulated  lobes.  But  .the 
largeft  is,  that  which  afcends  on  both  fides  out- 
wards from  the  fides  of  the  fella  turcica,  and  di- 
vides the  hemifpliere  into  two  lobes.  Upon  the  fur- 
face  of  thefe  lobes,  lies  the  cortex,  which  is  ex- 
tremely foft,  and  of  an  afh  colour,  tinged  with  yel- 
low or  red.  It  is  the  moft  tender  of  all  the  parts  in 
the  human  body.  The  internal  parts  are  occupied 
by  the  medulla,  which  is  almoft  white,  but  redder 
in  the  foetus  ; perforated  by  very  numerous,  recH- 
lineai  and  firnple  arteries,  more  folid  and  more  ca- 
pable of  fufcaining  its  hgure,  notwithfeanding  it  is 
very  foft,  and  in  greater  quantity  than  the  cortex. 
The  greater  pofierior  branch  of  the  carotid  artery 
(cccxvii.)  divides  each  hemifphereof  the  brain  in- 
to a fmailu'  aiiterior  lobe,  raid  a lamer  nollerior  lobe. 

CCCXLII. 


Chap.  X. 


BRAIN  AND  NERVES. 


159 

cccxLii.  The  fabric  of  the  cortex  was  long  a 
fubject  of  controverfy ; but  it  is  now  fafficientiy 
evident,  from  anatomical  injections,  that*  much  the 
greater  part  of  it  conhfts  of  veliels,  which  arife  in 
every  part  from  the  branches  of  the  pia  mater,  like 
footftalks,  enter  into  the  cortical  fubftance,  and 
convey  a fluid  thinner  than  blood  ; and  fometimcs, 
in  difeafes  from  ftranguiation,  and  in  animals,  efpe- 
ciaily  in  birds,  they  receive  even  the  true  blood- 
The  remaining  part  of  the  cortex  which  is  not  fill- 
ed by  any  injection,  is  probably  either  an  affemblage 
of  veins,  or  of  yet  more  tender  veffels  ; for  no 
diffimilarity,  which  would  lead  us  to  conjecture  one 
part  of  it  to  be  tubular,  and  the  other  part  folid, 
is  apparent  in  the  cortex,  in  its  healthy  hate.  Be- 
fides,  of  the  apparently  uniform  cortex,  a greater 
portion  becomes  vafcular  j the  greater  the  induftry 
which  has  been  employed  in  filling  the  veffels,  and 
the  greater  the  tenuity  of  the  injection.  The  idea 
of  its  being  glandular,  has  been  difcarded  by  uni- 
verfal  confent ; nor  indeed  was  there  ever  any  opin- 
ion received  with  lefs  probability  than  this. 

cccxLiii.  In  order  to  underftand  the  nature  of 
the  medulla,  we  are  to  confider  the  internal  ftruc- 
ture  of  the  brain,  compared  with  the  brains  of  brute 
animals  and  filh.  That  part  of  the  brain  which  lies 
immediately  under  the  external  convolutions,  is  of  a 
white  colour,  and  becomes  gradually  broader  and 
more  abundant ; fo  that  at  length,  it  compofes  the 
whole  oval  feclion  of  the  brain,  except  only  corti- 
cal covolutions  on* its  furface.  In  this  part,  the 
two  hemifpheres  of  the  brain,  which  I before  ob- 
ferved  were  not  entirely  divided,  are  united  by  a 
central  portion  of  medulla.  That  part  of  the  me- 
dulla which  lies  under  the  falciform  proceis,  but  at 
fome  diftance  from  it,  is  called  the  corpus  callo- 
fum  ; in  the  upper  furface  of  which  run  two  paral- 
lel white  ftripes,  formed  by  the  puKation  of  the  ar- 
teries, diverging  forwards,  and  terminated  at  the 

anterior 


BRAIN  Mm  NERVES. 


Chap.  S. 


i6o 

^interior  commifiure,  and  in  like  manner  divided 
backwards.  The  anterior  extremity  of  the  corpus 
callofum,  is  loft  in  the  fubftance  of  the  crura  cere- 
bri, comirtg  from  the  anterior  lobes  of  the  brain  : 
the  pofterior  extremity,  which  is  broader,  vdth  its 
ihorter  termination  bent  in  the  fliape  of  a talon,  pen- 
etrates inwards,  and  defcends  with  another  por» 
tion  into  the  inferior  horn  of  the  ventricle  ; and 
with  its  longer  termination  is  continued  into  the 
hippocampus.  Moreover,  the  whole  ftirface  of  this 
fubftance  is  ftreaked  with  tranfverfe  fibres,  which 
are  continued,  but  extenuated,  into  the  adjacent 
medulla  of  the  brain.  Even  its  interior  fubftance 
is  of  a ftriated  nature,  and  its  lower  furface  has  its 
raphe  and  tranfverfe  fibres. 

cccxLiv.  What  follows  is  more  difficult  to  be 
underftood  ; for  the  brain  is  not  folid,  but  from  the 
bottom  of  its  medullary  portion,  which  is  incum- 
bent UDon  the  multiform  bone,  where  the  jrreater 
crus  of  the  brain  pafles  out  from  it,  a cavity  com- 
mences, covered  only  with  the  pia  mater,  which 
gradually  afcends  backwards,  and  then  turriing,  con- 
tinues its  courfe  forwards  and  upwards.  Then  it 
divides  itfelf  near  the  pofterior  extremity  of  the 
corpus  callofum  ; and  vdth  its  fliorter  pofterior  por- 
tion it  ends  in  the  pofterior  lobe  of  the  brain, 
with  its  extremity  directed  inwards,  and  filled  vath 
the  talon  mentioned  above  ; but  its  anterior  portion 
is  extended  along  the  fide  of  the  corpus  callofum, 
parallel  to  the  horizon,  and  with  a horn  incrcafing 
in  breadth  outwards,  it  terminates  in  the  anterior 
lobe  of  the  brain.  The  cavity  thus  formed,  of 
which  there  is  one  in  each  hemdfphere  of  the  brain, 
and  which  do  not  communicate,  is  called  the  ven- 
triculus  anterior  or  tricornis.  It  is  naturally  filled 
with  vapour,  which  is  frequently  condenied  into 
water  or  ieliy. 

cccxLv.  This  cavity  has  no  vacuity,  for  the  upper 
and  lower  portions  of  the  brajn  mutually  touch  each 

other. 


Chap.  X.  BRAIN  AND  NERVES.  i6i 

other.  Below,  its  floor  is  varioufly  figured.  Ante- 
riorly, it  confifts  of  a horn,  having  in  its  lov/er  part 
an  eminence,  which  is  flightly  convex,  long,  diver- 
ges backwards,  is  covered  with  an  extremely  vafcu- 
lar  membrane,  and  is  outwardly  cinereous.  They 
are  called  the  corpora  ftriata ; becaufe  inwardly 
they  exhibit,  intermixed  with  much  cortical  fub- 
flance,  alternate  white  oval  ftreaks,  parallel  to  one 
another,  and  longer  behind,  befides  lefler  fpots  and 
points,  as  if  of  medullary  fubftance.  More  inwardly 
and  pofteriorly,  two  other  fimilar  eminences,  more 
of  an  egg  like  fliape,  towards  the  third  ventricle 
and  other  parts  in  a great  meafure  cinereous  on  the 
outfide,  and  obfcurely  ftriated,  incline  towards  each 
other,  fo  that  they  frequently  cohere  on  the  upper 
part,  by  the  intermixture  of  their  cortical  fubflance  : 
thefe,  going  inwards  and  defcending  through  the 
horn  of  each  anterior  ventricle  to  the  bails  of  the 
Ikull,  generate  the  optic  nerves,  of  which  they  are 
called  the  thalami.  Between  the  corpora  ftriata 
and  thalami,  there  is  an  intermiediate,  parallel,  and 
white  band  of  medullary  fubftance,  which  is  called 
the  centrum  femicirculare  geminum,  produced  from 
the  anterior  commiffure,  and  frequently  from  the 
crura  of  the  fornix  ; but  efpecially  from  the  me- 
dulla of  the  brain  itfelf,  before  the  thalami.  This 
commiflure,  which  is  broad  and  ftrong,  joins  togeth- 
er the  anterior  part  of  the  brain  before  the  thalami. 
The  centrum  geminum,  wdiich  is  broadeft  behind, 
arifes  with  many  fibres  from  the  jundlion  of  the  pes 
hippocampi  with  the  medulla  of  the  brain.  The 
corpora  ftriata,  with  the  thalami,  conftitute  the 
medullary  crura  of  the  brain  ; which,  in  the  bafts 
of  the  cerebrum,  pafs  over  the  medulla  of  the  cere- 
bellum, and  are  joined  together  at  the  anterior  ex- 
tremity of  the  bridge,  to  be  defcrlbed  hereafter. 
Where  they  approach  neareft  to  one  another,  each 
fends  out  an  hemifpherical  eminence,  called  mtamil- 
lary.  The  fibres  of  the  medulla  of  tlie  brain  itfelf, 
M interwoven 


i62  brain  and  nerves.  Chap.  X. 

interwoven  with  the  medulla  of  the  cerebellum, 
defcend  into  the  medulla  oblongata  ; and,  being- 
then  collected  into  a bundle,  they  go  to  the  corpo- 
ra pyramidalia. 

cccxLvi.  The  corpus  callofum  projects  in  the 
middle  over  the  common  axis  of  thofe  ventricles. 
Behind,  it  refts  contiguoufly  upon  the  fornix.  Be- 
fore, two  fimilar  medullary  partitions,  v'hich  are 
called  the  feptum  lucidum,  triangular,  united  be- 
low, with  their  vertex  inclined  backwards,  and  in- 
cluding an  anonymous  central  cavity,  defcend  from 
this  body  along  the  corpora  ftriata,  even  to  the 
union  of  the  thalami.  This  feptum  below  is  con- 
tinued to  the  fornix,  which  is  a ceiling  fupported  on 
four  pillars,  having  its  anterior  origin  from  the 
medulla  of  the  brain,  and  fometimes  from  the  ma- 
millary protuberances,  and  the  cornmiflure  which 
we  have  mentioned ; and  behind  that,  particularly 
under  the  thalami,  often  both  from  the  centrum  ge- 
rninurn  and  curved  line  of  the  thalami.  This  fornix 
is  incumbent  upon  the  interval  between  the  corpora 
feriata,  and  upon  the  interval  between  the  thalami ; 
and  degenerates  partly  into  a broad  thin  fimbria,  the 
pes  hippocampi,  where  it  is  divided  into  toes  ; and 
partly  into  other  tubercles,  which  are  continuous 
both  with  the  fornix  and  corpus  callofum,  but  more 
evidently  continued  from  the  latter,  as  larger,  and 
are  femi-cylindrical,  having  the  fimbria  attached  to 
them.  Thefe  defcend  into  the  lower  anterior  horns 
of  the  ventricles  ; and  at  lafi:  terminate  in  an  arch, 
convex  outwards, and  commonly  divided  by  ten  fur- 
rows, imprinted  on  it  by  the  convolutions  of  the 
brain,  and  in  a four  toed  hoof,  whence  the  name  of 
hippocampus,  which  is  externally  covered  by  an  ex- 
ceedingly thin  medullary  lamina,  but  internally 
confihs  of  cortical  fubftance.  At  the  beginning  of 
the  divifion  of  the  pes  hippocampi,  the  taenia  ends 
in  two  white  ftriee,  a long  and  a fliort  one,  inferted 
into  this  foot  and  into  the  brain,  or  in  one  inferted 

into 


Chap.  X. 


BRAIN  AND  NERVES. 


163 

into  the  moft  internal  unguis.  A like  protuberance, 
continuous  with  the  corpus  callofum,  enters  into 
the  pofterior  horn  of  the  ventricle,  crooked  imvards 
at  its  extremity,  like  the  fpur  of  a bird,  the  pofterior 
part  of  the  defcending  horn  of  the  ventricle  being 
occupied  by  a column  continuous  with  it.  Between 
the  diverging  pofterior  crura  of  the  fornix,  the  me- 
dullary portion,  which  is  behind  the  middle  plexus 
of  the  ventricles,  and  marked  generally  with  tranf. 
verfe  and  palmated  ftreaks,  is  called  the  pfalterium. 

cccxLvii.  In  the  anterior  and  lower  part  of  the 
ventricles,  on  each  fide,  begins  the  choroid  plexus, 
included  in  the  pia  mater  only,  lying  naked  in  the 
reft  of  the  ca\nty  of  the  fkull,  made  up  of  a great 
many  fmall  arteries  (cccxvii.  cccxviii.)  and  veins 
originating  from  the  large  trunk,  (cccxxv.)  all 
which  numerous  veflels,  joined  together  by  the  pia 
mater,  refemble  a curtain  varioufly  folded.  It  is 
often,  but  not  always,  intermixed  with  many  pel- 
lucid glands  of  a round  figure,  refembling  hydatids. 
It  afcends  from  the  bafis  of  the  brain,  through  the 
defcending  horn  of  the  ventricle,  and  becomes  dilat- 
ed as  it  proceeds  upwards  ; but  afterwards  becom- 
ing narrower,  it  goes  along  the  optic  thalamus,  to 
the  pofterior  extremity  of  the  feptum  luciduin. 
When  thefe  plexufes  have  reached  the  anterior  ex- 
tremity of  the  thalami,  they  cohere,  and  are  continu- 
ed with  a remarkable  vafcular  plexus,  which  gradu- 
ally defcends  along  the  roof  of  the  third  ventricle 
as  far  as  the  pineal  gland,  and  is  continued  into  the 
pia  mater  of  the  pofterior  lobes  of  the  brain.  From 
this  proceeds  the  internal  warmth  of  the  brain,  and 
it  undoubtedly  exhales  and  inhales.  The  choroid 
plexufes  are  very  broad  where  the  anterior  ventri- 
cles begin  to  defcend ; contracting  gradually  down- 
wards, they  projeff  in  the  inferior  anterior  end  of 
the  ventricle,  covered  only  by  the  pia  mater. 

cccXLviii.  Between  the  thalami,  applied  to  each 
other  almoft  with  a plain  furface,  there  is  a natural 
ra  2 fiffure. 


BRAIN  AND  NERVES. 


Chap.  X. 


i64 

liffure,  wnich  is  terminated  by  the  crura  of  the 
brain  meeting  together  in  the  bafis  of  the  fkuU  r 
this  is  called  the  third  ventricle.  It  leads  by  a per- 
pendicular funnel,  forwards  into  a cortical  column 
it  is  hollow  in  brutes,  lefs  evidently  tubular  in  man> 
and  connected  to  the  pituitary  gland. 

cccxLix.  This  gland,  flattened  on  both  fides^ 
Ample,  of  uncertain  ftruclurej  in  the  Interior  larger 
part,  almoft  round,  and  of  a reddifli  colour  ; in  the 
poiterioF  part  lefs,  cinereous,  tranfverfely  broad  ; 
covered  with  the  pia  mater  of  the  brain ; lies  upon 
a proper  deprefiion  of  the  feUa  turcica,  and  feems 
to  be  a kind  of  appendix  to  the  brain. 

cccL.  Backwards,  the  thalami,  are  conjoined  in 

the  bottom  of  the  ventricle,  by  a central  medullary 

fafeia,  or  pofterior  commiflure,  and  by  a fmaller 

trarifverfe  chord ; from  which,  on  each  Ade,  an 

arched  white  band  goes  out  in  the  upper  part,  which 

lofes  itfelf  in  the  centrum  geminum,  and  in  the- 

anterior  commiflure,  and  fometimes  in  the  crus 

©f  the  fornix.  On  the  fore  and  upper  part,  the 

thalami  have  a protuberance,  which  is  formed  by 

the  triansfular  fornix  Atuated  between  the  two  tha- 
o 

lami. 

cccLi.  This  eminence  feparates  the  upper  trian- 
gular cavity  of  the  third  ventricle.  Ailed  up  with 
the  fornix,  from  the  inferior  calamus  feriptorius^ 
fo  that  the  cavity  is  continued  both  to  the  anterior 
and  poflerior  extremity  of  the  third  ventricle,  from 
the  top  to  the  bottom.  But  the  anterior  commif- 
fure  is  alfo  a medullary  band  which  unites  the  tha- 
lami before  the  anterior  crura  of  the  fornix. 

cccLii.  For  a pofterior,  tranfv'erfe,  Agured  emi- 
nence is  applied  to  the  thalami,  which  conjoins  the 
medulla  of  the  right  and  left  pofterior  lobes  of  the 
brain.  It  is  marked  behind  by  four  oval  emi- 
nences, v'hich  are  outwardly  fmaller,  called  the 
nates  and  teftes,  and  which  confift  externally  of 
fome  medulla,  and  internallv  of  cortical  fubftance. 

The 


'Chap.  X. 


BRAIN  AND  NERVES. 


155 

The  {iiperior  ones  in  man  are  the  largeft,  and  are 
called  the  nates.  Upon  thefe  is  feated  a cortical 
gland,  ovally  conical,  fupplied  with  many  velTels,, 
into  which  the  choroid  plexus  degenerates  ; this  is 
the  celebrated  pineal  gland  fo  frequently  difeafed, 
which  is  joined  to  the  brain  by  fmail  footftalks  fent 
into  the  linea  alba  through  the  thalami  in  their  pat- 
fage  forwards.  Between  this  eminence,  marked 
with  thefe  four  protuberances,  and  the  crura  of  the 
medulla  oblongata,  a canal  refembling  an  aqueduct, 
and  manifeftly  open,  paffes  from  the  third  to  the 
fourth  ventricle. 

cccLiii.  The  whole  medulla  of  the  brain  below, 
is  collected  together  in  its  bahs,  into  two  very  thick 
compreffed  columns,  having  their  furface  longitu- 
dinally marked  with  lines,  and  conlifting  exter- 
nally of  medulla  with  fome  cortical  fubfiance  in- 
ternally. Thefe  are  the  crura  of  the  brain.  Thefe, 
meeting  together  backwards,  are  covered  by  the 
fubjacent  crura  of  the  cerebellum,  and  are  infert.- 
ed  by  apparent  ftrata  of  fibres  into  the  pyramidal 
bodies  of  the  medulla  oblongata ; and  with  other 
deeper  tranfverfe  fibres,  which  feparate  the  inner 
fibres  that  come  from  the  cerebellum  from  the 
preceding,  conftitute,  together  with  the  medulla 
cerebelli,  the  beginning  of  the  medulla  oblongata, 

cccLiv.  The  cerebellum,  as  it  is  lefs,  fo  it  is 
more  fimpie  than  the  brain.  It  has  two  lobes,  but 
no  where  deeply  parted,  united  above  and  below 
by  a central  ring  of  the  fame  fabric  with  itfelf, 
ealled  the  vermis,  at  the  fide  of  which  there  is  a 
broad  fmooth  eminence  of  the  fame  nature  with 
the  cerebellum.  This  part  of  the  encephalon  con- 
tains a great  deal  of  the  cortical,  and  little  of  the 
medullary  fubfiance.  And  here,  likewife,  the  cor- 
tex is  placed  in  the  circumference,  but  marked 
with  furrows,  which  are  mofdy  parallel,  fo  as  to 
form  circular  arclies.  Thus  the  lobules  are  defin- 
ed. 


BRAIN  AND  NERVES. 


Chap.  X. 


1 66 

ed.  but  not  deeply,  each  of  which  contains  its 
medulla,  and  by  tlie  gradual  union  of  many  of  thefe 
medullary  branches  into  one  trunk,  an  arbufcular 
appearance  is  produced.  This  luedulla,  coHecled 
together  into  the  large  crura  of  the  cerebellum,  and 
internally  marked  with  ferrated  and  intricate  cor- 
tical lines,  has  a threefold  termination.  One  part 
afcends  towards  the  bafis  of  the  nates,  where  it 
joins  the  medulla  of  the  brain  under  the  teftes  ; 
and  the  right  is  alfo  joined  to  the  left  by  a tranf- 
verfe  medullary  band  behind  the  nates.  From 
this,  fome  dillinct  fibres  afcend  outwards,  and  join 
themfelves  to  the  tranfverfe  ones  of  the  bridge. 
Between  thefe  firft  prccelies  of  the  cerebellum,  is 
flretched  a medullai-y  lamina,  behind  the  fourth 
ventricle,  fending  forth  fibres  beyond  the  procefs. 
The  fecond  portion  defeends  into  the  fpinal  mar- 
row, and  terminates  in  peculiar  ftudded  protuber- 
ances, having  other  cortical  protuberances  adjacent, 
both  of  which  are  anonymous.  The  third  portion, 
which  is  larger,  and  fituated  in  the  middle,  going 
tranfverfely  dovmwards,  pafles  under  the  crura  of 
the  brain,  which  it  embraces  ; and  being  twice 
alternated  with  their  medullary  fibres,  (ccclii.)  by 
its  own  tranfverfe  fibres,  it  is  in  a great  meafure 
blended  with  them. 

cccLv.  Thus,  from  the  crura  of  the  brain  dc- 
feending  over  thofe  of  the  cerebellum,  and  from  the 
medulla  of  tlie  cerebellum  tranfverfely  furround- 
ing that  of  the  cerebrum,  there  is  produced,  in  the 
firft  place,  the  pons,  vrhich  is  almofi;  oval,  but  more 
flattened  on  both  fides,  deprefled  in  the  middle, 
and  every  where  marked  with  tranfverfe  fibres. 
Then,  continuous  v.ith  the  pons,  the  medulla  ob- 
longata is  formed,  vTiich  is  internally  variegated 
and  fireaked  with  feme  cortical  fubftance,  is  of  a 
conical  fliape,  and  defeends  directly  to  the  great 
foramen.  This  meduila  has  two  pairs  of  tubercles 
before  the  pons  j the  outerinofi;  of  the  figure  of 

an 


Chap.  X. 


BRAIN  AND  NERVES. 


167 

an  olive,  and  the  innermoft  of  a pyramidal  flrape, 
diminilhing  conically  downwards  : thcfe  are  divid- 
ed in  the  middle  by  a furrow,  into  which  the  pia 
mater  enters.  But  betwixt  this  medulla  and  the 
vermiform  procefs  of  the  cerebellum,  is  formed  a 
cavity,  limited  by  the  four  lelfer  proceifes,  which 
afeend  and  defeend ; at  firft  it  is  narrower,  but  above 
the  tubercles  (cccliv.)  it  grows  broader,  and  is  of 
a rhomboidal  figure  : it  is  called  the  fourth  ven- 
tricle, and  is  fhut  behind  by  the  valvula  magna,  or 
medullary  velum,  which  unites  the  procefles  going 
from  the  cerebellum  to  the  nates,  and  the  vermis, 
with  the  tranfverfe  band  lying  under  the  teftes, 
and  fliuts  the  ventricle  behind,  (cccliv.)  This 
ventricle  has  a moderate  furrow,  bounded  on  each 
fide  by  tumiid  edges,  inferibed  on  the  medulla  ob- 
longata, and  correfponding  to  a canal  which  is 
covered  by  the  nates  and  teftes,  and  is  called  the 
aqueduct,  (cccxlviii.)  In  this  laft  ventricle,  as  in 
the  foregoing,  there  is  a plexus  choroides,onlylefs, 
and  a fulcus  called  calam.us.  Each  of  thefe  fulci  is 
continued  down  along  the  m.edulla  fpinalis,  the 
anterior  moft  evidently,  the  pofterior  lefs  fo.  In 
the  former,  tranfverfe  fibres  are  detached  from  the 
right  to  the  left  fide,  both  in  the  medulla  oblon- 
gata and  fpinalis.  But  two  or  three  of  the  trlnf- 
verfe  ftreaks  of  the  fourth  ventricle,  terminating 
in  the  foft  nerve,  arife  from  the  eminences  inclof- 
ing  the  fulcus  ; others  go  to  the  eighth  pair,  and 
others  of  the  fame  kind  afeend  to  the  crus  of  the 
cerebellum. 

cccLvi.  All  the  medulla  of  the  brain  and  cere- 
bellum paftes  out  from  the  flcull,  through  different 
openings,  to  the  places  for  which  it  is  deftined. 
The  fmaller  bundles  of  this  medulla  we  call  nerves  ; 
but  the  larger,  Avhich  is  a continuation  of  the  ob- 
longata, we  call  the  medulla  fpinalis.  The  nerves 
are  medullary  fafciculi,  very  foft  in  their  origin, 
and  compofed  of  chords  of  fibres  meeting  from  the 

brain, 


i68 


BRAIN  AI'JD  NERVES. 


Cmap.  X, 


brain,  even  there  in  fome  examples,  dihinct,  ftraight 
and  parallel  in  the  nerve.  Thele  chords,  after  hav- 
ing proceeded  fome  way,  and  being  covered  with 
the  pia  mater,  which  is  fomewhat  red  and  firm, 
are  united  into  a more  conftant  fafcia  ; and  then, 
conjoined  with  others  of  the  fame  kind  by  cellular 
membrane,  divided,  and  contiguous,  go  on  to  their 
proper  opening  in  the  dura  mater,  and  run  along 
its  canals  and  intervals,  till  they  meet  with  an  open- 
ing in  the  ikull,  out  of  which  they  pals  through  a 
funnel  of  the  dura  mater.  The  nerve,  having  ar- 
rived without  the  ficull,  is  commonly  furrounded 
by  the  dura  mater,  and  becomes  folid  and  firm. 
This  is  the  cafe  in  the  optic  nerve,  in  the  fifth  pair, 
and  in  others  ; but  in  fome  again  there  does  not 
appear  to  be  any  dura  mater  furrounding  the  nerve, 
as  in  the  olfacfory  nerves,  in  the  foft  portion  of  the 
auditory  nerve,  and  the  intercofcal.  The  nerves, 
now  naked  and  lefs  defended,  amongft  the  mufcles, 
are  compofed  of  chords,  each  of  which  has  its  medul- 
la, and  its  flreath  of  pia  mater.  The  ultimate  cht>rds 
of  this  kind  unite  into  other  larger  chords, furround- 
ed by  much  ceilular  fubflance,  through  which  run 
many  frnall  arteries  and  veins  ; and  fometimcs  fat 
itfelf  is  depofited.  But  the  general  covering,  com- 
mon to  the  whole  nervous  bundle,  is  formed  by 
fome  indurated  cellular  fubftance,  often  refembling 
a true  membrane,  which  envelopes  them  all,  and 
combines  them  into  one  nerve. 

cccLvii.  I'he  whole  of  the  nerves  of  the  head 
arife  from  the  lower  part  of  the  medulla  of  the  brain 
or  cerebellum.  The  olfacfory  nerve  arifes  by  a lat- 
eral fibre  from  the  interval  betwixt  the  anterior 
lobes  of  the  brain,  and  by  a direct  fibre  from  the 
medulla  of  the  anterior  lobe  itfelf.  A great  part  of 
the  optic  nerve  fprings  from  the  thalami,  (cccxlv.) 
but  fome  part  likewife  from  the.  crus  of  the  brain, 
v/hiie  the  nerves  decullate  it.  The  third  pair  arifes 
from  the  bottom  of  the  crus  of  the  medulla  of  tlic 

brain. 


Chap.  X. 


BRAIN  AND  NERVES. 


169 

brain,  behind  the  mamillary  proceffes.  The  fourth, 
whether  funple  or  bifid,  proceeds  from  the  fide  of 
the  procefs  of  the  cerebellum  to,  the  teftes.  The 
fifth  arifes  plainly  from  the  peduncles  of  the  cere- 
bellum. The  fixth  from  the  bottom  of  the  pons, 
from  the  deep  fulcus  (cccliv.)  between  it  and  the 
meduUa  oblongata.  The  feventh  arifes  with  one 
portion,  which  is  fofter,  pofterior  and  larger,  from 
the  medulla  oblongata,  and  by  two  tranfverfe  ftriae, 
from  the  fourth  ventricle  itfelf  ; and  with  another 
harder  portion,  from  that  part  of  the  crus  of  the 
cerebellum  next  the  pons.  The  eighth  from  the 
interval  between  the  corpora  olivaria  and  pyrami- 
dalia,  out  of  a furrow  of  the  medulla  oblongata  ; 
and,  according  to  the  obfervation  of  other  eminent 
anatomifts,  from  the  fourth  ventricle  itfelf.  The 
ninth  arifes  from  the  corpora  olivaria  and  pyrami- 
dalia.  The  tenth  is  a nerve  of  the  neck,  as  appears 
from  its  double  root,  its  conjunclion  with  the  up- 
per and  lower  adjacent  nerves,  and  its  place  of  ori- 
gin. Therefore,  no  nerves  arife  properly  from 
the  cerebellum,  unlefs  the  fifth  and  fourth  ; for  the 
anterior  nerves,  the  olfactory,  optic,  and  third 
pair,  come  from  the  brain  only  ; and  all  the  reft 
from  thofe  parts  where  the  medulla,  both  of  the 
brain  and  cerebellum,  are  conjoined. 

cccLviii.  The  fpinal  marrow  is  a veiy  foft  me- 
dullary rope,  which  defcends  from  the  medulla 
oblongata,  as  low  as  the  fecond  vertebra  of  the 
loins.  In  the  neck  it  is  fiat  before  and  behind,  and 
gibbous  at  the  fides  ; in  the  back  it  is  almofl;  qua- 
drangular. It  is  largefi  where  it  goes  out  from  the 
head ; from  thence  it  becomes  fmaller  in  the  top 
of  the  neck,  then  larger  at  its  lower  part ; again  it 
is  fmaller  throughout  almofi:  the  whole  back,  but 
thicker  at  bottom  ; and  laftly,  it  ends  in  tubercles, 
one  conical,  another  oval.  Like  the  brain,  it  is  in- 
vcfied  with  its  own  pia  mater,  which  enters  deeply 
into  its  anterior  filfare,  and  almofi:  divides  the  me- 
dulla 


BRAIN  AND  NER  v^S. 


Chap,  X. 


170 

dulla  into  two.  Within  it  has  fome  obfcure  cortical 
fubftanee  ; its  anterior  artery  arifes  in  the  Ccull, 
from  the  branches  of  the  vertebrals  ; it  is  retro- 
grade, defcending  through  the  whole  length  of  the 
pia  mater,  perpetually  making  alternate  hnuous 
flexures,  forming  inofculations  about  many,  but  not 
all  of  the  nerves,  with  branches  of  the  vertebral, 
intercoftal,  lumbar,  and  facral  arteries  ; till  at  laft, 
covered  v/ith  a peculiar  coat  from  the  pia  mater,  it 
goes  out  at  the  coccyx  and  difappears.  Two  pof- 
terior  arteries,  flmilar,  but  fmaller,  arife  from  the 
lower  arteries  of  the  cerebellum  : thefe  are  more 
ferpentine,  and  have  frequent  mutual  inofculations. 
The  fpinal  veins  accompany  the  arteries  in  their 
defeent  from  the  brain  itfelf,  and  fend  out  branches 
m like  manner,  accompanying  the  nerves  into  as 
many  circular  iinufes,  fituated  in  the  dura  mater, 
as  there  are  vertebree,  all  of  which  fo  communicate 
one  with  another,  that  each  communicates  with 
thofe  above  and  below  it,  by  a flraight  duct,  in  each 
direction,  and,  by  a branch  fent  outwards,  unites 
with  the  vertebral,  intercoflal,  lumbar,  and  facral 
veins.  The  uppermoft  of  thefe  fmufes  inofeuiates 
with  the  anterior  occipital  finufes,  (ccclii.) 

cccLix.  But  the  fpinal  marrovr  is  furrounded 
by  another  covering,  loofely  and  at  fome  diflance, 
which  is  not  vaicular,  but  pellucid  like  water,  tol- 
erably firm  and  continued  from  the  brain.  It  is 
called  arachnoid,  is  longer  than  the  pia  mater,  be- 
ing extended  to  the  bottom  of  the  os  facrum,  and 
there  it  alone  includes  the  bundle  of  contiguous 
nerves.  But  in  what  manner  it  accompanies  the 
nerves  in  their  paffage  out,  has  not  been  hitherto 
deferibed.  Between  that  membrane  and  the  dura 
mater,  there  is  a vapour,  which  is  frequently  con- 
denfed  into  a reddifh  water,  and  produces  a true 
dropfy. 

cccLx.  Lafdy,  the  dura  mater  of  the  fpinal  mar- 
row is  continuous  with  that  of  the  brain,  furrounds 


Chap.  X, 


BRAIN  AND  NERVES. 


171 

the  araclinoides,  in  like  manner  defcends  to  the  bot- 
tom of  the  os  facrum,  larger  at  its  beginning,  at  the 
bottom  of  the  neck,  and  at  the  loins,  but  flenderer 
in  the  back,  and  at  laft  terminates  in  a llender 
cone,  attached  by  many  ligaments  to  the  periof- 
teum  of  the  os  facrum.  As  the  nerves  pafs 
through  this  membrane,  it  gives  them  an  external 
covering,  which  direclly  enlarges  with  them  into  a 
ganglion,  or  hard,  oval,  reddilh  knot.  To  this  dura 
mater  in  the  intervals  between  ail  the  nerves,  a den- 
ticulated ligam.ent  internally  adheres,  which  arifes 
from  the  Ikull  near  the  paffage  of  the  ninth  pair  of 
nerves,  and  connects  the  arachnoid  to  the  dura  ma- 
ter by  triangular  produftions,  in  each  of  the  inter- 
vals, between  the  anterior  and  potter ior  bundles  of 
the  nerves  down  to  the  bottom,  and  twelfth  verte- 
bra of  the  back.  Externally,  the  dura  mater  is 
furrounded  by  fome  lubricating  fatty  matter,  and 
then  by  the  internal  covering  of  the  vertebrae,  which 
are  themfelves  fo  conttrucfed  into  a canal,  that  the 
fpinal  marrow  is  not  compretted  by  it  in  any  of  its 
flexions. 

cccLxi.  The  fibres  of  the  fpinal  marrow  appear 
diftincl  in  dropfical  fubjetts,  and  in  brute  animals. 
Thefe  arife  from  the  whole  anterior  and  potterior 
furfaces  of  the  fpinal  marrow  ; and  commonly  the 
anterior  chords  included  in  the  pia  mater,  converge 
like  rays  into  a larger  fafciculus  ; to  which  a fimilar 
falciculus  of  the  potterior  filaments  accedes,  form- 
ing one  nerve,  which,  patting  out  through  a hole  of 
the  dura  mater,  between  every  two  vertebrae,  pro- 
duces a nerve.  The  vertebral  nerves  are  about  30 
in  number.  In  the  neck,  numerous  radiated  ner- 
vous fibres  compofe  one  large  and  almott  tranfverfe 
nerve.  In  the  back,  they  defcend,  in  general, 
fmaller  j but  10  that  the  lower  and  larger  ones  are 
commonly  contiguous  to  one  another.  The  large 
and  long  lumbar  ones  join  to  form  the  cauda  equina. 
The  lowett  nerves  of  the  os  facrum  are  very  fraall. 


BRAIN  AND  NERVES. 


Chap.  X. 


172 

the  uppermoll  ones  large.  Many  of  the  dorfal 
nerves,  together  with  the  lumbar  and  facral  ones, 
covered  v/ith  their  proper  pia  mater,  accompanied 
by  their  arteries,  and  inciofed  in  the  arachnoid 
membrane,  conftitute  that  chord  which  is  called  the 
cauda  equina. 

cccLxii.  Thofe  nerves  are  dlftributed  to  all  parts 
of  the  body  in  a very  complicated  manner,  which 
does  not  admit  of  a defeription  in  this  place.  But 
the  following  particulars  cannot  be  palled  over.  All 
the  fpinal  nerves,  except  one  or  two  in  the  neck, 
after  palling  out  of  the  vertebrae,  have  botli  an 
anterior  and  pofterior  trunk.  The  former  is  fent 
tO"  the  mufdes  only.  The  latter  forms  a ner- 
vous root,  which  joining  with  its  fellows,  and  vvitli 
a fmall  accelfory  branch,  which  comes  through  the 
pterygoid  canal,  from  the  fixth  nerve  of  the  brain, 
and  the  fecond  branch  of  the  fifth,  forms  one  of  t!ie 
principal  nerves  of  the  humian  body  ; which,  com- 
municating; with  almofl  ail  tlie  other  nerves  of  the 
whole  fyftem,  fends  out  nervous  branches  to  the 
heart,  and  to  all  the  vifeera  of  the  abdomen.  It  has 
as  many  ganglia  as  it  has  roots  from  the  fpinal  mar- 
row, unlefs  when  feveral  of  them  join  into  one  gan- 
glion. It  communicates  varicully  with  the  crural, 
braclaial,  and  diaphragmatic  nerves,  alfo  with  the 
par  vagum  and  ninth  pair.  Another  principal  nerve 
is  the  eighth  or  par  vagum,  arifing  from  the  brain, 
and  joining  iifelf  to  the  intercoftal  in  the  bottom 
of  the  neck,  in  the  thorax,  and  in  the  abdomen  ; 
this  paffes  out  of  the  Ikuil  in  three  chords,  of  which 
the  larger  fends  branches  to  the  larynx,  throat,  the 
cardiac  plexufes  themTelves,  (xcix.)  lungs,  cefopha- 
g*us,  ftomach,  and  liver.  The  third  of  thefe  is  the 
phrenic  nerve,  arifing  from  mod  of  the  lower  nerves 
of  the  neck,  and  having  received  an  augmentation 
from  the  brachial  nerves,  and  fometimes  from  the 
root  of  the  ninth,  it  delcends  along  the  pericar- 
dium, and  inferts  itfelf  into  the  upper  furtacc  of 
the  diaphragm  j below,  it  is  iiippiied  from  tlie 


Chap.  X. 


BRAIN  AND  NERVES. 


173 

great  plexus  of  the  intercoftal  nerve.  Laflly,  the 
acceffory  nerve,  arifing  by  many  fmali  roots  from 
the  fix  or  feven  uppermoft  pofterior  cervical  nerves, 
and  from  the  medulla  oblongata,  returning  into  the 
fkull,  joins  the  eighth  pair  and  feems  to  produce 
fome  Sympathy  betvdxt  that  important  nerve  and 
the  fpinal  marrow:  Finally,  tlie  nerves  of  the 

limbs  originate  from  plexufes,  and  are  on  account 
of  their  length,  harder  and  larger,  than  the  nerves 
%vhich  go  to  the  vifcera  ; thofe  which  go  to  tlie 
hand,  arife  from  the  four  lower  nerves  of  the  neck, 
and  firft  and  fecond  of  the  back ; thofe  of  the  low- 
er extremities  from  the  nerves  of  the  loins  and  os 
facrum. 

cccLxiv.  The  nerves  divide  into  branches  like  the 
blood-^veilels,  but  in  acute,  and  often  manifeftly  ret- 
rograde, angles,  growing  gradually  fofter  and  fmall- 
er,  though  fometirnes  they  become  thicker,  as  tliey 
recede  from  the  brain  ; at  length,  with  their  ulti- 
mate extremities,  which  are  INdom  vifibie,  feem  to 
terminate  in  a pulp,  by  depofiting  the  firm  integu- 
ments with  which  they  were  covered,  after  the  man- 
ner which  we  obferve  in  the  optic  nerve.  But  the 
rectilineal  courfe  of  the  fibres,  continued  from  the 
brain -itfelf,  is  fuch,  that  they  are  never  divided  in 
any  ramification,  but  only  recede  from  each  other, 
where  they  had  been  connected  by  cellular  fub- 
llance.  This  appears  from  diforders,  confined  to 
fome  particular  parts,  not  extended  to  the  whole, 
produced  by  affections  of  the  brain  ; as  a lofs  of 
the  voice,  deafnefs,  dumbnefs,  and  palfies  of  par- 
ticular mufcles.  They  are  connefted  by  cellular 
fubffance  to  the  adjacent  parts,  have  hardly  any 
elafticity ; do  not  contrad  on  being  divided,  but 
only  expel  their  medulla  by  the  contradion  of  their 
integuments.  In  whatever  way  they  are  irritated, 
they  do  not  contrad,  nor  are  they  rendered  fhorter 
during  the  motion  of  the  mufcles  which  they  ex- 
cite. A great  many  nerves  are  fent  into  the  muf- 

des  j 


BRAIN  AND  NERVES. 


Chap.  X. 


m 

cles  ; many  to  the  Ikin  ; fewer  to  the  vifcera  ; very 
few  to  the  lungs  ; and  none  to  the  dura  or  pia  ma- 
ter, arachnoides,  tendons,  capfules,  ligaments,  and 
lailly  the  whole  fecondary  membranes.  Like  the 
veffels,  they  make  frequent  anaftomofes  with  each 
ether,  or  out  of  one  trunk  they  are  divided  into  ma- 
ny branches  : and  it  is  principally  in  the  concourfe 
of  branches,  arihng  from  different  trunks,  that 
the  ganglia  are  found.  Thefe  are  hard  nervous 
tumors,  for  the  moil:  part  vafcular,  and  included  in 
a iirm  membrane,  of  which  the  ufe  and  ftructure  are 
uncertain,  and  in  which  the  ftraight  courfe  of  the 
nervous  fibres  is  interrupted.  They  are  not  found 
in  the  nerves  of  the  fenfes,  or  in  the  eighth  pair ; 
or  in  the  phrenic  nerves  ; or  in  the  nerves  of  the 
extremities  ; but  are  peculiar  to  the  fpinal  nerves, 
to  the  intercoftal,  which  is  in  fact  a fpinal  nerve, 
and  to  the  fifth  pair. 

cccLxv.  Theie  are  nearly  what  we  have  learned 
from  anatomy  concerning  the  brain  and  nerves  ; 
the  phyfxological  ufes  of  thefe  parts  remain  to  be 
inveffigated.  Every  nerve  which  is  irritated,  by 
whatever  caufe,  produces  an  acute  fenfe  of  pain. 
Senfation  is  a change  of  the  miind,  produced  by  a 
change  of  the  body.  It  is  the  medullary  part  of 
the  nerve  which  feels.  If  a nerve  be  appropriated 
to  any  peculiar  fenfe,  that  fenfe  perifhes  when  the 
nerve  is  compreffed  or  divided  ; and  the  fenhbility 
of  the  whole  body  is  deftroyed,  when  the  brain  is 
compreffed  ; or  of  thofe  parts  whofe  nerves  origi- 
nate below  the  feat  of  preffure,  if  you  comprefs  the 
fpina.1  marrov/.  If  certain  parts  of  the  brain,  from 
which  particular  nerves  arife,  be  compreffed,  then 
thefe  fenfes  only  are  loff,  as  the  fight  or  hearing. 
Thofe  parts  of  the  body  which  receive  nerves,  pol- 
fefs  fenfibility  moft  acutely,  when  they  receive 
many,  as  the  eyes  and  penis  ; obtufely,  when  they 
receive  few  nerves,  as  the  vifcera ; and  thofe  which 
have  no  nerves,  as  the  dura  mater,  tendons,  liga- 
ments, 


Chap.  X,  BRAI^T  AND  NERVES.  175 

ments,  fecundlnes,  the  broad  bones,  and  cartilages, 
have  no  fenfation. 

ccci-xvi.  It  is  extremely  probable,  that  all  fen- 
fation  arifes  from  the  imprefiion  of  a fenllble  objeS: 
on  fome  nerve  of  the  human  body ; and  that  the 
fame  being  tranfmitted  to  the  brain  along  that 
nerve,  is  at  laft  reprefented  to  the  mind,  after  it 
has  reached  the  brain.  It  therefore  feems  to  be 
falfe,  that  the  mind  perceives  immiediately  by  means 
of  the  fenforia  and  branches  of  the  nerves.  For 
this  opinion  is  refuted,  by  the  pains  felt  after  am- 
putation, by  the  entire  ceffation  of  pain  when  a 
nerve  is  compreffed,  and  by  the  difeafes  of  the 
fenfes  from  injuries  of  the  brain.  That  the  effe& 
of  the  fenfes  is  preferved  in  the  brain,  is  evident 
from  the  lofe  of  memory  which  fucceeds  compref- 
fions  or  injuries  of  the  brain  ^ alfo  from  the  deli- 
rium which  happens  in  fome  difeafes,  and  the  ftu- 
por  and  lleepinefs  which  happen  in  others.  We 
have  already  obferved,  that  the  dura  mater  has  no 
fenfation. 

cccLXvii.  Another  office  of  the  nerves  is  to  ex- 
cite the  mufcles  into  powerful  action.  When  a 
nerve  is  irritated,  the  mufcle  to  which  it  goes  is 
immediately  convulfed  ; or  the  mufcles,  if  it  fend 
branches  to  feveral.  This  happens  during  the  life 
of  the  animal,  and  a little  after  its  death  w'hile 
all  the  parts  are  Rill  moift.  By  great  irritation, 
other  mufcles  are  thrown  into  convullions,  and 
even  the  whole  body.  Nor  is  it  necelTary  that 
the  nerve  fhould  be  entire  ; for  even  when  it  is 
cut,  on  being  irritated,  it  will  excite  limilar  mo- 
tions in  the  mufcles.  On  the  other  hand,  when  a 
nerve  is  compreffed  or  tied,  a palfy  follows  ; for 
the  mufcles  which  have  their  nerves  from  that  one, 
lie  unmoved,  when  they  are  commanded  by  the 
will  to  act.  They  again  recover  their  mobility, 
when  the  compreffion  is  removed,  provided  the 
nerve  has  received  no  injury. 


CCCLXVIII* 


BRAIj^J  Al'JD  NERVES. 


Chap.  X. 


1‘jG 

cccL  XVIII.  When  the  medulla  of  the  brain  is 
deeply  wounded  or  irritated  in  its  crura,  dreadful 
convulsions  enliie  throughout  the  whole  body  ; the 
difference  of  the  part  irritated  produces  no  ex- 
ception ; nor  does  the  brain,  cerebellum,  or  corpus 
callofum,  enjoy  any  perogative  in  this  rcfpcct. 
The  fame  confequences  follow,  if  the  fpinal  mar- 
row be  irritated.  But  if  the  encephalon  itfelf  be 
compreffed,  in  any  part  whatever,  there  enfues  a 
lofs  of  lenfe  and  motion  in  fome  part  of  the  body, 
which  appears  to  be  exactly  that  which  has  its 
nerves  from  the  part  compreffed,  according  to  ob- 
servations of  injuries  of  particular  portions  of  the 
brain,  in  which  the  orivinof  the  nerves  beinsr  com- 
preffed,  the  voice  is  loft  ; or  the  motion  of  one  arm 
or  leg,  or  of  one  fide  of  the  pharynx.  In  injuries  of 
the  fpinal  marrow,  it  is  ftiU  more  evident,  that  thofe 
parts  v/hich  receive  their  nerves  from  the  place  in- 
jured, are  convulfed  if  that  be  irritated,  or  rendered 
paralytic  if  it  be  comprefled.  But  when  any  more 
confiderable  portion  of  the  braiti  is  compreffed, 
cither  from  blood,  water,  feirrhus,  an  impacted 
bone,  or  other  mechanical  caufe,  the  greateft  part, 
or  the  whole  of  the  body,  lofes  its  power  of  mo- 
tion ; the  voluntaiy  organs,  if  the  lefion  be  in  a 
lefs  degree,  and  all  of  them  vv'hen  it  is  greater ; ail 
theie  diforders  ceafe  upon  removing  the  compref- 
fing  caufe.  Laftly,  if  the  fpinal  marrow  in  the 
neck  be  injured,  death  quickly  enfues  ; bccaufe, 
from  that  part  the  nerves  of  the  heart  (xcix.)  prin- 
cipally arife. 

cccLxix.  Thefe  things  being  confidered,  there 
feems  to  be  no  doubt,  that  ail  motion  in  the  human 
body, proceeds  in  a great  meafure  from  thebrain,and 
its  annexed  cerebellum  and  fpinal  marrow ; and  that 
it  is  thence  conveyed  through  the  nerves,  to  all  the 
mufcles  and  parts  of  the  body.  Befides,  the  caufe 
of  motion  cannot  rchde  in  the  parts  themfelves,  fince 
it  would  then  remain  after  the  brain  is  deftroyed, 

and 


Chap.X.  brain  and  nerves.  177 

and  would  not  be  increafed  by  irritating  the  brain, 
or  weakened  by  comprehing  it. 

cccLxx.  Is  there  in  the  brain  any  principal  part, 
which  is  the  origin  of  ail  motion,  the  end  of  all 
fenfation,  and  where  the  foul  has  its  feat  ? Is  this 
proved  by  the  frequent  obfervation  of  the  integrity 
of  the  fenfes,  and  power  of  motion  remaining  after 
fevere  injuries  of  the  brain  ? Is  it  in  the  corpus 
callofum  ? Is  this  fhewn  by  the  greater  mortality  of 
wounds  or  difeafes  in  the  corpus  callofum  ? Is  this 
body  fufficiently  connected  with  the  nerves  ? Are 
there  any  experiments  which  derive  from  it  the 
fifth,  feventh,  and  other  nerves  ? Does  not  the 
fame,  or  even  greater  mortality,  accompany  wounds 
of  the  medulla  fpinaiis  ? Yet  this  is  not  the  feat  of 
the  foul,  fince,  though  it  is  compreffed  or  even  de- 
firoyed,  the  perfon  will  furvive  a long  time,  with 
the  perfect  ufe  of  all  his  fenfes.  Nay  this  opinion 
is  oppofed  by  numerous  fafts  ; birds  have  no  cor- 
pus callofum  5 and  wounds  in  that  body,  are  not 
in  the  leaft  more  mortal  than  thofe  in  other  parts  of 
the  brain,  as  appears  from  undoubted  experiments. 

cccLxxi.  Nor  does  the  cerebellum  enjoy  the 
prerogative  of  exciting  the  vital  aftions,  nor  are 
the  provinces  of  vitality  and  animality  diftinct ; 
nor  does  the  cerebellum  generate  the  nerves  of  the 
heart  and  other  vital  organs,  and  the  brain  thofe 
which  go  to  the  organs  of  fenfe  and  voluntary  mo- 
tion. From  the  cerebellum  the  fifth  nerve  is  moil 
evidently  produced  ; but  that  goes  to  the  tongue, 
pterygoid,  buccinator,  temporal,  and  frontal  mufcles, 
the  ear,  the  eye,  the  noftrils,  all  which  are  parts 
either  moved  by  the  will,  or  deftined  for  fenfe. 
Again,  the  fame  nerve,  as  the  eighth,  fends  vital 
branches  to  the  heart  and  lungs,  animal  and  volun- 
tary ones  to  the  larynx,  and  fenfitive  ones  to  the 
ftomach.  Laftly,  it  is  not  even  true,  that  diforders 
of  the  cerebellum  occafion  death  fo  certainly  and 
fpeedily.  For,  from  certain  obfervations,  even  of 
N our 


178  BRAIN  AND  NERVES.  Chap.  X. 

our  own  making,  it  has  borne  wounds  and  fcirrhi, 
without  taking  away  life  ; nor  is  it  very  different 
from  the  brain,  being  only  fofter  and  more  tender  ; 
and,  laftly,  we  read,  and  that  not  very  rarely,  of 
wounds  of  the  cerebellum  being  cured.  The  power, 
however,  of  this  part,  in  exciting  convulfions,  is 
fomewhat  greater. 

cccLxxii.  Concerning  the  feat  of  the  foul,  we 
mufl  inquire  experimentally.  In  the  firft  place,  it 
muft  be  in  the  head,  and  not  in  the  fpinal  marrow. 
For  though  the  latter  be  affected,  the  integrity  of 
the  mind  remains  the  fame.  Again,  it  appears, 
from  the  experiment  of  con%nilfions  arifing  v/hen 
the  inmolt  parts  of  the  brain  are  irritated,  that  it 
lies  not  in  the  cortex,  but  in  the  meduUa  ; and  not 
improbably,  in  the  crura  of  the  medulla,  the  cor- 
pora ftriata,  thalami,  pons,  medulla  oblongata,  and 
cerebellum.  Finally,  by  another  not  abfurd  con- 
iecture,  it  lies  at  the  origin  of  every  nerve,  fo  that 
the  concurrence  of  the  firft  origins  of  all  the  nerves, 
makes  up  the  cenforium  commune.  Are  the  fen- 
fations  of  the  mind  reprefented  there,  and  do  the 
voluntary  and  neceffary  motions  arife  in  thatpkce? 
This  feems  very  probable.  For  it  does  not  feem 
pofiible,  that  the  origin  of  motion  can  lie  below 
that  of  the  nerve  ; for  that  would  be  a gratuitous 
fuppofition  of  immobility  or  infenfibility,  in  fome 
part  of  the  nerve,  though  perfectly  ftmilar  to  the 
reft.  Nor  can  the  origin  of  motion  (cccnxix.)  be 
placed  higher  in  the  arteries,  for  they  neither  have 
feeling,  nor  are  excited  to  voluntary  motion.  It 
therefore  follows,  that  the  feat  of  the  mind,  muft 
be  where  the  nerves  firft  begin. 

O , - 

cccLxxiii.  We  come  now  to  the  explanation  of 
the  manner  in  which  the  nerves  are  the  organs  of 
fenfe  or  motion ; which,  as  it  lies  hid  in  the  ulti- 
mate elementary  fabric  of  the  medullary  fibres, 
feems  to  be  placed  above  the  reach  both  of  our 
fenfes  and  rcafon : but  we  fhaii  endeavour  to  make 


Chap.  X.  BRAIN  AND  NERVES. 


179 

as  great  an  approximatfon  to  the  truth  as  polhble, 
by  experiments.  Firft,  it  is  demonilrated,  that 
fenfation  does  not  come  through  the  membranes 
from  the  fentient  organ  to  the  brain,  and  that  mo- 
tion is  not  tranfmitted  through  the  coverings  from 
the  brain  into  the  mufcle.  For  the  brain  itfelf, 
deeper  than  thefe  membranes,  receives  the  impref- 
lions  of  fenfe,  and  when  injured  throws  the  mufcles 
into  convulhcns.  Moreover,  it  is  certain,  that  the 
nerves  arife  from  the  medulla  of  the  brain  ; the 
truth  of  which  is  manifeft  in  all  the  nerves  of  the 
brain,  more  efpecially  in  the  olfaflory,  optic,  fourth 
and  feventh  pair,  which  continue  their  m.edullary 
fabric  a long  way  before  they  receive  the  covering 
of  the  pia  mater. 

cccLXxiv.  We  muft,  therefore,  Inquire  into  the 
nature  of  this  medulla.  It  is  a very  foft  pulp, 
harder  in  infects  and  idiots  ; in  other  refpects  every 
where  alike.  It  is  difpofed,  however,  to  be  formed 
into  fibres,  or  parallel  threads,  lying  upon  one  an- 
other lengthwifej  This  appears  from  innumerable 
obfervations,  efpecially  in  the  corpus  callofum,  cor- 
pus ftriatum,  thalami  of  the  optic  nerves,  fpinal 
marrow,  in  the  brains  of  filhes,  and  efpecially  in 
their  thalami  opticL  Again,  that  the  fibres  of  the 
brain  are  continuous  with  thofe  of  the  nerves,  fo 
as  to  form  one  continued  fubftance,  appears  very 
evidently  in  the  feventh,  fourth  and  fifth  pair  of 
nerves.  There  is  a great  deal  of  oil  in  the  medul- 
la, upwards  of  a tenth  part  of  its  whole  weight. 

cccLxxv.  But  here  a controverfy  begins  con- 
cerning the  nature  of  this  fibre,  which,  with  other 
fimilar  fibres,  compofes  the  fubftance  of  the  medul- 
la and  of  the  nerves.  Many  recent  philofophers 
have  fuppofed  it  to  be  a folid  thread,  and  only  moif- 
tened  by  vapour  exhaling  into  the  cellular  fabric 
which  furrounds  the  nervous  fibres,  and  that,  when 
it  is  ftruck  by  a fenfible  body,  the  vibration  excit- 
ed is  conveyed  to  the  brain. 

N 2 


CCOLXXVI, 


BRAIN  AITD  NER\^S. 


Chap.  X, 


?8o’ 

cccLxxvi.  But  the  phenomena  of  wounded 
nerves  will  not  allow  us  to  imagine  the  nervous 
fibres  to  be  folid.  For,  if  a nerve  when  irritated, 
vibrate,  (after  the  manner  of  an  elaftic  chord,  which 
trembles  when  it  is  taken  hold  of,)  the  nerve 
ought  to  confiil  of  hard  fibres,  fixed  by  their  ex- 
tremities to  hard  bodies,  and  tenfe  ; for  chords 
which  are  foft,  or  not  tenfe,  or  not  fixed,  do  not 
vibrate.  But  all  the  nerves,  at  their  orign,  are 
medullary,  and  very  foft,  and  exceedingly  far  from 
any  kind  of  tenfion  ; and  they  retain  the  fame  foft 
texture,  and  arc  not  covered  with  membranes, 
where  they  pafs  through  w^ell  protected  channels, 
as  the  intercoftal  nerve  and  the  fecond  branch  of 
the  fifth  pair  ; fome  alfo  are  foft  throughout  their 
whole  length,  whatever  fize  they  may  be  of  ; . as, 
for  example,  the  foft  olfactory  and  acouftic  nerves, 
in  w^hich  laft  we  would  molt  readily  expect  tre- 
mor ; as  in  found.  Agadn,  although  the  nerves  be 
hard,  they  become  foft  in  the  vifeera,  mufdes,  and 
fenfogia,  before  they  act.  Therefore,  the  nervous 
fibres,  being  neither  tenfe  in  their  origin,  nor  in 
their  termination,  cannot  pofilbly  vibrate  in  an 
elaftic  manner.  But  alfo,  in  particular  and  moft 
important  cafes,  they  cannot  vibrate  ; becaufe, 
through  their  whole  length,  they  are  firmly  tied 
to  folid  parts,  by  means  of  cellular  fubftance  ; for 
example,  the  neiwes  of  the  heart  are  tied  to  the 
great  arteries,  and  to  the  pericardium.  Finally, 
that  the  nerves  are  totally  devoid  of  elafticity,  is 
demonftrated  by  the  experiment,  in  \vhich  the 
nerves,  cut  in  two,  neither  become  fhorter,  nor 
draw  back  their  divided  ends  to  the  folid  parts  ^ 
but  are  rather  elongated  from  their  laxity,  and  ex- 
pel their  medulla  in  form  of  a protuberance.  Be- 
lides,  the  extremely  foft  medulla  of  the  brain  ex- 
hibits aU  the  phenomena  of  pain  and  convulfions, 
which  are  produced  by  nerves,  without  any  pofli- 
bilitv  of  tenfion. 


cccLssvn. 


Chap.X.  brain  and  nerves,  I8i 

cccLxxvii.  Add  to  this,  that  the  motion  of  an 
irritated  nerve  is  propagated  downwards,  and  that 
mufcles  that  are  feated  above  the  place  of  irrita- 
tion, are  never  convulfed.  This  is  altogether  in- 
confiftent  with  elafticity  j for  an  elaftic  chord  prop- 
agates its  tremors  from  the  point  of  percuffion,  to 
both  extremities.  Bnt,  if  the  phenomena  of  fenfe 
and  motion  cannot  be  explained  from  the  nature  of 
elafticity,  the  only  probable  fuppofition  that  re- 
mains is,  that  there  is  a liquor  which  comes  from  the 
brain,  defcends  into  the  nerves,  and  flows  out  to  the 
extreme  parts  of  the  body ; the  motion  of  which 
liquor,  accelerated  by  irritation,  operates  only  ac- 
cording- to  the  direction  in  which  it  flows  ; and  the 
convulfions  cannot  afcend  upwards,  becaufe  of  the 
reftftance  made  by  the  frefh  afflux  of  the  fluid  from 
the  brain.  But  the  fame  liquid  being  put  in  mo- 
tion in  an  organ  of  fenfe,  by  a fenftble  body,  tranf- 
mits  its  motion  upwards  to  the  brain  ; for  then  it  is 
not  refifted  by  a contrary  fenforial  torrent  coming 
from  the  brain. 

cccLxxviii.  It  is  therefore  probable,  that  the 
nervous  fibrils,  and  the  medullary  fibres  of  the 
brain,  which  have  the  fame  nature,  are  hollow. 
Nor  is  the  fmallnefs  of  thefc  tubes,  which  are  not 
vifible  by  any  microfcope,  of  any  force  againft  the 
propofed  arguments  j nor  the  abfence  of  fwelling 
in  a tied  nerve,  which  is  not  exaflly  true  ; with 
other  arguments  of  the  like  kind,  v/hich  indeed 
fliow  the  weaknefs  of  our  fenfes,  but  have  not  any 
validity  againft  the  real  exiftence  of  nervous  fluids. 
If  they  are  tubes,  it  is  very  probable  that  they  de- 
rive their  fluids  from  the  arteries  of  the  brain. 

cccLxxix.  Eut  the  nature  of  this  fluid  is  dif- 
puted.  Many,  efpecially  the  moderns,  will  have 
it  to  be  extremely  hard  or  elaftic,  ethereal,  or  even 
electrical  ; but  the  more  ancient  opinion  is,  that 
it  is  rather  aqueous,  incompreflible,  and  albumi- 
nous. Indeed  it  is  not  to  be  denied,  that  there  are 

many 


i82 


BRAIN  AND  NERVES. 


Chap.  X. 


many  arguments  againfl  admitting  either  of  thefe 
opiaions.  An  eledrical  matter  is,  indeed,  the  moft 
po'^terful,  and  litteft  for  exeiting  motion  ; but  then 
it  cannot  be  confined  within  the  nerves,  but  pene- 
trates throughout  the  whole  animal  to  vhich  it  is 
commuuicated,  and  fiUs  with  its  energy  the  flelh 
and  fat,  as  well  as  the  nerves.  But,  in  a living 
animal,  the  nerves  only,  or  fuch  parts  as  are  pej’- 
vadcd  by  nerves,  tremble  when  irritated  ; and, 
therefore,  this  liquid  muft  be  of  a nature  which 
permits  it  to  flow  through  the  nerves,  and  yet  con- 
fines it  within  their  tubes.  Alfo  a ligature  on  a 
nerve  takes  away  fcnfe  and  motion,  but  does  not 
flop  an  elecirical  current. 

cccLXXX.  A watery  and  albuminous  nature  is 
common  to  miofl  of  tlie  juices  in  the  human  body, 
and  may  be  therefore  readily  imagined  to  exift  in 
the  nervous  fluid,  as  indicated  by  the  water  which 
exudes  into  the  ventricles  of  the  brain  from  the 
fame  veflels  ; by  the  gelatinous  fluid,  which  flows 
out  in  cutting  through  the  brain  in  fifh,  and  the 
larger  nerves  of  animals  ; and  by  the  tumor  which 
a riles  in  tied  nerves*  But  is  fuch  a nature  capable 
of  explaining  the  wonderful  force  of  commlfed 
nerves,  obfervable  in  the  difleclions  of  living  ani- 
mals, even  the  fmalleft,  and  in  the  great  ftrength 
of  mad  and  liyfterical  people  ? Is  the  hydroflatic 
example  of  capillary  tubes  of  any  n'eight ; which, 
althougli  it  may  explain  the  ftrength  in  the  mo- 
ticHi,  is  neverthclefs  inconiiflent  with  the  celeri- 

... 

cccLxxxi.  For,  the  nervous  fluid,  which  is  the 
inflrement  of  fenfe  and  motion,  muft,  be  exceed- 
ingly moveable,  fo  as  to  carry  the  impreflions  of 
feiife,  or  commands  of  the  mill,  to  the  places  of 
their  ddti nation,  without  any  imaginable  lofs  of 
time,  and  cannot  receive  the  caufe  of  its  motions 
only  from  the  heart.  Moreover,  it  is  very  thin  and 
invlfible,  and  dcititute  of  all  tafte  and  fmcll  ; yet 

reparable 


• Chap.  X. 


BRAIN  AND  NERVES. 


•183 

reparable  from  the  aliments.  It  is  not  on  any  ac- 
count to  be  confounded  with  that  vifible,  vifcid 
liquor  exhaling  into  the  intervals  of  the  nervous 
chords. 

cccLxxxii.  That  this  liquor  moves  through 
tubes  rather  than  through  the  fpongy  and  folid 
fubftance  of  the  nerves,  we  are  perfuaded  from  its 
celerity,  and  from  the  analogy  of  the  whole  body  ; 
of  which  all  the  liquids,  the  fat  excepted,  how 
through  their  proper  veffels. 

cccLxxxiii.  Therefore,  upon  the  whole,  it  feems 
to  be  certain,  that,  from  the  veffels  of  the  cortex, 
a liquor  is  fecreted  into  the  hollow  tubes  of  the 
medulla,  which,  being  continued  into  the  fmall 
tubes  of  the  nerves,  and  propelled  to  their  extremi- 
ties, is  the  caufe  both  of  fenfe  and  motion.  But 
there  will  be  a twofold  motion  in  that  humour  ; 
the  one  how  and  conftant,  from  the  heart ; the 
other  not  continual,  but  exceedingly  fwift,  which 
is  excited  either  by  fenfe,  or  any  caufe,  as  motions 
arifmg  in  the  brain. 

cccLxxxiv.  The  fame  nerves  moh  evidently 
are  fubfervient  both  to  fenfe  and  motion  ; fo  that 
we  are  not  allowed  to  adopt  two  diftinfl:  fyhems  of 
nerves,  one  motory,  the  other  fenfitive.  If  fenfe 
fometimes  remains  after  motion  is  deftroycd,  this 
feems  to  be  becaufe  much  more  hrength  is  required 
for  the  latter.  Dying  people  hear  and  fee,  when 
incapable  of  motion. 

cccLxxxv.  What  becomes  of  this  nervous  huid, 
which  cannot  but  be  fecreted  in  very  great  abun^ 
dance,  from  fo  large  a quantity  of  blood  moved 
with  fuch  velocity,  if  you  compare  it  with  the  very 
copious  fecretion  from  more  ffuggihi  blood,  and  at 
a greater  dihance  from  the  heart,  in  the  fmall  re- 
nal and  mefenteric  arteries  ? It  is  not  improbable 
that  it  exhales  through  the  cutaneous  nerves  ; the 
laffitude,  fupervneing  in  a few  hours  both  to  fen- 
fation  and  motion,  and  its  removal  by  fpirituous 

medicines, 


BRAIN  AND  NERVES. 


Chap.  X. 


184 

inedicines,  fhew  that  this  liquid  may  both  be  loft 
and  repaired.  Many  have  thought  that  it  alfo 
exhales  into  various  cavities  of  the  body  ; as  that 
of  the  ftomach,  and  inteftines.  Vfe  may  expect 
fomc  part  of  it  to  be  abforbed,  that  the  nobleft 
fluid  of  the  body  may  not  be  too  quickly  diflipated. 
That  it  nourifhes  the  body,  is  improbable  : it  is 
too  moveable  to  expect  adhelion  from  it : that  is 
the  office  of  flow  and  vifcid  fluids. 

cccLxxxvi.  What  is  the  purpofe  of  fo  many 
protuberances  in  the  brain  ; of  the  ventricles,  nates, 
and  teftes  ; of  the  diftinction  of  the  brain  from  the 
cerebellum  ; and  of  fo  many  tranfverfe  chords  com- 
municating from  one  fide  of  the  brain,  cerebellum, 
and  fpinal  medulla,  to  the  oppofite  fide  ? 

cccLXXxvii.  The  diftindion  of  parts  neceflary 
for  important  ufes,  feems  to  have  produced  the  ne- 
ceffity  of  the  ventricles.  That  the  corpora  ftriata 
and  thalami  might  keep  their  medulla  diftinct,  it 
was  neceflary  for  a vapour  to  be  interpofed  be- 
tween them  ; and  the  fame  reafoning  is  true  with 
regard  to  the  brain  and  cerebellum.  Perhaps,  like- 
wife,  the  ncceiiity  of  introducing  warmth  into  the 
thick  medulla  of  the  brain,  may  have  produced  the 
neceffity  of  a cavity  through  whicli  the  arteries 
may  enter  in  great  numbers  and  crowded  together. 
Perhans  alfo  it  was  proper,  that,  into  the  inmoft 
parts  of  the  brain,  fmall  veffels  only,  without  any 
large  ones,  hiould  enter.  We  may  alfo  fufpect, 
that  the  foftnefs  of  the  fibres  of  the  brain  requires 
fiiortnefs,  in  order  to  fuftain  their  own  weight. 

cccLxxxviii.  We  are  not  yet  acquainted  vith 
the  ufes  of  moft  of  the  protuberances,  and  we  ought 
to  learn  them  from  difeafes,  and  from  anatomical  ex- 
periments made  on  animals  refembiing  man.  But  we 
have  little  hopes  of  fuccefs,  in  parts  that  are  fo 
final],  fo  deeply  fituated,  and  hardly  ever  to  be 
touched,  without  inflicling  a fatal  wound.  Do  fo 
many  diftince  provinces  of  ideas  exift  in  them  j as. 


Chap.  X.  brain  and  nerves.  185 

in  the  optic  thalami  ? But  moft  of  thefe  protuber- 
ances produce  no  nerves. 

cccLXXxix.  The  internal  bands  and  duels  feem 
to  make  fome  communication  of  motions,  and  per- 
haps of  fenfations.  Some  of  thefe  join  the  brain 
with  the  cerebellum  ; others  join  the  fpinal  mar- 
row with  the  nerves  of  the  brain,  as  the  accelfory 
nerve  ; and  moft  of  them  join  the  right  and  left 
parts  together,  as  the  anterior  commilTure  (cccxlv.) 
and  the  two  pofterior  (cccl.)  the  corpus  callofum 
(cccxniii.)  the  flrias  between  the  procefs  from  the 
cerebellum  to  the  teftes  (cccliv.)  and  the  medullary 
crofs  bars,  in  the  bottom  of  the  third  ventricle,  and 
in  the  medulla  oblongata  and  fpinalis  (ccclv.)  For 
this  manifeilly  feems  to  be  the  reafon  why,  as  in 
inlinite  examples,  from  an  injury  of  the  right  fide 
of  the  brain,  the  \vhole  mufcles  of  the  left  fide  of 
the  body  become  paralytic,  and  the  reverfe  al- 
though it  feems  unaccountable,  that  this  decuflation 
does  not  ahvays  happen.  Moreover,  by  this  con- 
trivance, nature  feems  to  have  provided,  that,  when 
any  part  of  the  brain  is  injured,  the  nerve  arifing 
from  it  is  not  always  rendered  ufelefs.  For  if  a 
nerve  receive  its  fibres,  both  from  its  own  hemifi. 
phere  of  the  brain,  and  from  the  oppofite  one,  by 
communicating  bundles,  its  office* may,  in  fome 
meafure,  be  continued  entire  by  the  fibres  which 
it  receives  from  the  oppofite  fide,  after  thofe  of  its 
own  fide  are  defiroyed.  Accordingly,  we  have 
numberlefs  infiances  of  wounds  of  the  brain,  even 
attended  with  a confiderable  lofs  of  fubfiance,  which 
yet  have  not  been  followed  with  permanent  injury 
to  any  nerve,  or  to  any  of  the  mental  faculties. 
Many  of  the  other  appearances,  fuch  as  the  fmaller 
firipes,  refemblances  of  nerves,  and  even  protuber- 
ances, are  produced  in  the  brain  from  mechanical 
neceffity,  the  pulfation  of  the  veffels,  and  the  figure 
of  the  incumbent  parts. 


cccxc. 


i86 


MUSCULAR  MOTION.  Chap.  XL 


cccxc.  We  have  faid,  that  the  nerves  are  the  or- 
gans of  fenfe  and  motion  ; we  fliall  therefore  pro- 
ceed firft  to  explain  motion,  becaufe  it  is  more 
fimple,  uniform  and  perpetual,  as  it  exills  in  the 
foetus  before  moll  of  the  fenfes. 


C H A P.  XI. 

MUSCULAR  MOTION. 

cccxci.'  I ‘HE  organ  of  motion  in  the  human 
^ body  is  not  hngle.  And,  in  the  firft 
place,  in  every  animal  and  vegetable  fibre,  in  hair, 
feathers,  membranes,  cellular  fubftance,  in  the  hu- 
mid mufcular  fibre,  and,  laftly,  in  animal  and  vege- 
table gluten,  there  is  acontracfilc  power,  by  which 
they  both  refill  extenfion,  and,  w'hen  the  extending 
power  is  taken  away,  acquire  their  former  Ihortnefs ; 
nor  does  this  power  ever  ceafe  endeavouring  to 
bring  the  elementary  particles  into  the  clofeft  con- 
ta<T  the  mechanifm  of  the  part  can  admit.  After 
death,  even  for  many  days,  it  does  the  fame,  fo  that 
the  fibres  of  a divided  mufcle  contract  towards  each 
extremity,  and  leave  a wide  gap  in  the  middle  ; al- 
fo  arteries,  when  divided,  contract  themfeives  in 
length. 

O 

cccxcii.  I call  this  force  dead,  becaufe  it  con- 
tinues to  acl  after  death,  and  fo  far  is  difierent  from 
the  po^vers  of  life.  In  the  living  animal  indeed  it 
is  fomewhat  more  lively  ; for,  both  from  cold  and 
fear,  the  fein  is  Ilimulatcd,  fo  that  it  grows  harder, 
and  erefled,  and  along  with  this  hardnefs  contracts 
itfeif  in  length.  Again,  the  cellular  fibres  are  per- 
petually endeavouring  to  iliorten  themfeives,  and 
always  tend  to  their  own  contraflion.  Hence,  when 
the  Hun  or  any  other  membrane  is  extended,  as 
foon  as  the  caufe  of  extenfion  is  taken  off,  it  returns 
by  a gentle  effort  to  its  former  Ihortnefs.  But  it 

allb 


Chap.  XI.  MUSCULAR  MOTION. 


187 

alfo  refills  diflention  in  another  way,  -with  a perpe- 
tual effort ; and,  by  a gentle  but  continual  approxi- 
mation of  its  own  elements,  it  propels  the  contain- 
ed fat  or  M^ater,  or  other  bodies  accidentally  intro- 
duced. The  fame  power  alfo  feems  to  limit  the 
excretion  of  vapour ; for  when  the  fibres  and  plates 
of  the  cellular  texture  are  preternaturally  relaxed, 
an  immenfe  quantity  either  of  fat  or  of  watery  hu- 
mour is  depofited  in  that  texture.  This  debility 
feems  to  be  the  principal  caufe  of  a true  dropfy. 
The  fame  caufe  being  always  efficacious,  and  at 
work  in  the  heart,  joints,  and  every  where  through- 
out the  body  of  the  embryo,  brings  into  nearer 
contact  tlie  arteries,  auricles,  and  ventricles  j pro- 
duces flexures  ; and  contrails  the  heart,  when  in  a 
manner  diffolved,  into  a cone.  By  an  unknown  or 
hidden  power,  it  alfo  feems  to  determine  the  fhape 
of  mofi;  parts  of  the  human  body ; by  expelling  the 
gluten  received  into  the  cells,,  bringing  the  terreflrial 
particles  nearer  to  one  another,  and  giving  the  pro- 
per folidity,  curvature,  and  fituation,  to  the  differ- 
ent parts. 

cccxciii.  It  Is  the  nature  of  this  power  to  afl 
continually,  by  a gentle  but  uninterrupted  effort. 
It  is  common  for  it  alfo  to  be  excited  by  poifons,  in 
every  membrane,  fibre,  and^  cellular  texture  ; but 
never  by  cutting  or  punfluring  with  a lharp  inffru- 
ment.  Thefe  are  the  proper  charafleriffics  of  the 
red  mufcular  fibre.  The  ftrufture  of  this  fibre  it 
is  now  neceffary  for  us  to  confider. 

cccxciv,  Mufcular  fibres  in  the  human  body, 
are  bundles  of  red  threads,  by  which  manifeft  mo- 
tion is  performed.  When  many  of  thefe  fibres  are 
collected  together,  and  are  evidently  red,  they  are 
called  a mufcle.  The  extreme  fimpiicity  of  the 
fabric  has  been  the  caufe  of  the  obfcurity  that  pre- 
vails in  underffanding  how  fmall  and  foft  flefliy 
fibres  can  produce,  with  fuch  ftrength,  moft  cxten- 

five 


m 


MUSCULAR  MOTION.  Chap.  XL 

five  motions,  both  in  man,  and  moft  efpecially  in 
the  cruftaceous  infects. 

cccxcv.  In  every  mufcle  there  are  fibres,  which 
are  long,  flender,  foft,  fomewhat  eiaftic,  aimoft  con- 
ftantly  parallel  on  the  whole,  and,  furrounded  with 
a good  deal  of  cellular  fubftance,  are  collected  into 
lacertuli.  Thefe  bound  together,  by  loofe  cellular 
fubftance,  generally  with  fome  fat,  unite  into  larger 
bundles,  which  are  always  divided  by  cellular  bands, 
and  membranous  partitions,  till  at  laft  a number 
of  them,  either  parallel  or  inclined,  furrounded 
with  a thin  cellular  membrane,  continuous  with 
their  partitions,  and  feparated  from  the  neighbour- 
ing mufcles  by  fome  coarfer  cellular  fubftance,  con- 
flitute  a lingle  mufcle.  In  every  vifible  fibre  there 
appears  a feries  of  filaments,  which,  by  oblique 
extremities  being  mixed  and  agglutinated  with  oth- 
ers of  the  fame  kind,  are  combined  into  one  larger 
fibre. 

cccxcvi.  The  generality  of  mufcles,  but  efpe- 
cially all  thofe  which  are  inferted  into  bones,  and 
all  which  are  preffed  ftrongly  by  other  flefliy  in- 
cumbent parts,'  do  not  confift  of  fibres  of  one  kind. 
For  the  flefhy  fibres  (cccxcv.)  being  collected  to- 
gether, commonly  compofe  the  fwelling  in  the 
middle  of  the  mufcle,  which  is  called  its  belly  : 
thefe  fibres  degenerate  by  degrees  at  each  end  of 
the  mufcle,  become  more  flender  and  hard,  and 
having  laid  afide  their  red  colour,  acquire  a filveiy 
fplendor,  and  being  compreffed  clofer  together,  are 
included  in  a fmaU  quantity  of  fnort  cellular  fub- 
ftance, are  coloured  with  fewer  veflels,  and  become 
indolent  and  fcarcely  irritable  : they  are  denominat- 
ed tendons  if  they  arc  collected  into  a narrow  round 
chord,  but  if  into  a broad  flat  furface,  aponeuroles. 
The  cellular  texture  which  covers  the  whole  ten- 
don is  called  its  vagina,  and  refembles  the  coat  of 
a mufcle.  That  flefliy  fibres  actually  change  into 
tendinous,  is  rendered  probable  by  comparing  the 

foetus, 


Chap.  XL  MUSCULAR  MOTION.  l^ 

foetus,  in  which  there  are  very  few  tendons,  with  a 
young  perfon,  in  whom  there  are  many  more  ; and 
with  an  adult  or  old  perfon,  in  whom  are  the  great- 
eft  number.  Mufcles  which  are  not  inferted  into 
any  bone,  have  commonly  no  tendons,  as  the  heart, 
the  fphinclers,  the  tongue,  and  mufcular  membranes 
of  the  vifcera  and  veffels.  But  thofe  commonly 
end  in  long  tendons,  which  are  required  to  pafs 
round  the  joints  and  heads  of  the  bones,  and  in 
that  extremity  which  is  njoft  moveable.  In  the 
foetus  the  mul'cles  are  evidently  inferted  into  the 
periofteum  only  ; but  in  adults,  where  the  periof- 
teum  is  intimately  united  with  the  bone,  the  ten- 
dons being  blended  with  the  periofteum,  adhere 
into  the  pits  of  the  bone  itfelf. 

cccxcvii.  The  tendinous  fibres  indeed  often  lie 
in  a ftraight  line  with  the  fieftiy  ones,  and  are,  as 
it  were,  a continuation  of  them.  But  it  is  not  at 
all  rare  for  the  flelhy  fibres  to  be  obliquely  inclined 
to  the  tendon,  and  to  adhere  to  it,  fo  that  it  grows 
thicker  in  its  progrefs  by  continually  receiving  new 
fibres.  This  is  called  a pennated  mufcle.  Other 
tendons  lie  in  the  middle  betwixt  two  plates  of 
fibres,  one  on  each  fide,  meeting  together  in  an  ob- 
tufe  angle  downwards.  There  are  jnftances  of  fev- 
eral  tendons  pennated  on  each  fide,  being  conjoin- 
ed into  one-  mufcle.  There  are  alfo  other  modes 
of  union  of  the  tendinous  with  the  fieftiy  fibres. 

cccxcviii.  Within  the  cellular  tunic  that  fur- 
rounds  the  fibres,  the  arteries  and  veins  are  fubdi- 
vided  into  rectangular  reticulations,  for  the  mofl 
part  accompanying  and  contiguous  to  each  other  ; 
thence  the  vapour  and  fat  effufed  into  the  coarfe 
and  fine  cellular  fubftance  ; thence  their  abforption. 
Lymphatic  veffels  run  along  the  mufcles  of  the 
tongue,  neck  and  face,  but  are  difficultly  demon- 
ftrated  in  the  limbs.  Along  with  the  blood-veffels, 
nerves  are  alfo  diftributed  throusch  the  cellular  lub- 
ftance  of  the  mufcles,  more  numeroufly  than  to 

other 


MUSCULAR  MOTION.  Chap.  XI. 


X90 

other  parts  of  the  body,  except  the  eye  ; they  lay 
afide  their  hard  involucrum,  become  fofter  and  van- 
ifh  before  they  can  be  traced  to  their  ultimate  ex- 
tremities. They  enter  the  fame  mufcle  in  many 
parts,  without  preference  to  any  particular  one. 
in  the  tendons  they  cannot  be  demonftrated.  Nor 
are  there  any  nervous  fibres  which  furround  and 
conftrinffe  the  mufcular  lacerti.  Thofe  who  have 
defcribed  them  faw  nothing  but  cellular  fubilance. 

cccxcix.  The  ftrucfure  of  the  ultimate  fibre, 
confidered  as  the  elements  of  a mufcle,  vrhen  in- 
veftigated  by  the  microfcope  in  man  and  other  an- 
imals, has  always  appeared  fimilar  to  the  liruclure 
of  the  larger  fibres  ; and  except  very  minute  fila- 
ments, connefted  by  cellular  fabftance,  nothing  up- 
on which  we  can  rely  has  been  obferved.  There 
is  no  feries  of  veficles  or  chain  of  rhombs.  Are 
thefe  fibres  hollow  ? Are  they  continuous  Avith  the 
arteries  ? Does  the  difference  betwixt  mufcular  and 
tendinous  fibres  confift  in  the  latter  being  rendered 
folid  by  being  comprefied  and  having  their  fluids 
expelled  ? That  the  blood  is  not  concerned,  is  prov- 
ed by  the  flendernefs  of  the  fibres,  vffiich  are 
fmaller  than  the  blood  globules,  by  the  whitenefs  of 
the  mufcles,  after  the  blood  is  waflaed  from  them, 
and  by  phyfiological  reafons  (ccccxr.)  And,  in  gen- 
eral, more  ftrength  may  be  expected  from  a folid 
fibre. 

cccc.  A mufcle  is  endowed  at  leaft  with  a three- 
fold power.  Firft,  the  dead  one,  common  to  it 
with  other  animal  fibres.  Then  another,  which 
vre  have  called  the  vis  infita,  poffTefiing  different 
plienomena.  For,  in  the  firft  place,  it  is  peculiar 
to  life,  and  to  the  firff:  hours  after  death,  and  it  dif- 
appcars  much  fooncr  than  the  dead  one.  Again, 
in  moll  cafes,  its  action  confifts  in  alternate  ofcilla- 
tions  ; fo  that  moving  to  and  fro,  at  one  moment 
it  contracts  itfelf  towards  the  middle  ; and  at  the 

next, 


Chap.  XI.  MUSCULAR  MOTION. 


191 

next,  extends  itfelf  from  the  middle  towards  the  ex- . 
tremities,  and  fo  on  fucceffively  for  feveral  times. 
Moreover,  it  is  manifeft,  quick,  and  performs  veiy 
confiderable  motions  ; the  dead  force,  only  fuch 
as  are  linail  and  fcarcely  apparent.  It  is  excited 
both  by  the  touch  of  a lharp  inftrument,  and  in  the 
hollow  m.ufcles  by  inflated  air,  by  water,  and  every 
kind  of  acrimony,  but  more  powerfully  than  by 
any  other  ftimulus  by  electricity.  Laftly,  it  is  pe- 
culiar to  the  mufcular  fibre,  and  in  no  other  part 
of  the  human  body  is  it  found  pofieiTed  of  the  qual- 
ities above  mentioned.  But  its  phenomena  deferva 
to  be  more  particularly  explained. 

cccci.  It  is  natural  to  every  mufcle  to  flrorten  it- 
felf, by  retracting  its  extremities  towards  its  belly 
or  middle.  In  order  to  difcover  the  moving  power 
from  the  fabric  which  we  have  defcribed,  it  will 
be  of  ufe  to  coniider  the  phenomena  of  mufcular 
contraction.  Every  mufcle  when  in  action  becomes 
fliorter  and  thicker.  This  contraction  of  its  length 
is  various  ; lefs  in  fome,  more  in  others  5 and  in 
particular  inftances  very  confiderable,  for  example, 
in  fome  of  the  fphinfters*,  iris,  diaphragm  and  inter- 
coftals,  infomuch  that  it  appears  that  the  length  of 
a mufcle  may  be  contracted  much  miore  than  one 
third,  which  computation  was  derived  from  an  er- 
roneous hypothefis. 

ccccii.  The  inteftines  are  exceedingly  tenadoms 
of  their  vis  infita  ; they  continue  to  contract,  after 
they  are  taken  out  of  the  body,  and  even  after  they 
are  cold.  The  heart  is  even  more  tenacious  than 
thefe,  if  you  confider  all  things  ; as  is  molt  evident 
in  the  chick,  and  in  cold  blooded  animals..  Differ- 
ent mufcles  are  moff  readily  excited,  by  different 
ftimuli ; as  the  bladder  by  urine,  the  heart  by  the 
blood,  and  the  inteftines  by  air.  Though  their 
nerves  are  removed,  on  their  Connexion  with  the 
brain  cut  off,  mufcles  lofe  but  little  of  their  irri- 
table nature.  It  appears  alfo,  that  this  irritable 

difpofitioa 


MUSCULAR  MOTION.  Chap.  XL 


ig2 

difpofition  is  very  widely  extended  through  the  an- 
imal fibre,  from  the  e:?iamp]es  of  polypi  and  other 
infefts,  which  have  neither  brain  nor  nerves,  and 
yet  are  exceedingly  impatient  of  any  fcimulus  ; and 
from  the  analogy  of  plants,  of  which  very  many 
flowers  and  leaves  open  or  eontraU,  according  to 
the  various  degrees  of  heat  and  cold,  fome  even  fo 
quickly,  that  they  are  nothing  inferior  in  this  refpecl 
to  animals.  This  power  is  totally  different  from 
any  other  known  property  of  matter,  and  is  new. 
It  does  not  depend  cither  upon  gravity,  or  attrac- 
tion, or  elafticity,  for  it  is  inherent  in  foft  fibres, 
and  is  deftroyed,  when  they  become  indurated. 

cccciii.  But  that  a caufe  of  motion  is  conveyed 
through  the  nerves  into  the  mufcles,  is  certain  from 
the  obfervations,  already  noticed  (ccclxvii.  et  feq.) 
For  the  nerve  alone  pollefies  feeling ; alone  conveys 
the  dictates  of  the  mind  ; and  neither  retains  any 
influence  over,  nor  receives  any  perceptions  from 
any  part,  whofe  nerve  is  either  tied  or  cut,  or  which 
lias  no  nerve.  On  irritating  the  nerve  or  fpinal 
marrow,  even  in  a dead  animal,  the  mufcle  or  muf- 
cles, which  have  nervous  branches  from  thoie  parts, 
are  moll  violently  convulfed.  When  the  nerve  of 
any  mufcle  is  cut  or  tied,  or  the  part  of  the  fpinal 
marrow,  or  brain,  from  whence  the  nerve  has  its 
origin,  is  compreffed,  the  mufcle  becomes  paralytic 
and  feeble,  and  cannot  by  -any  power  be  recalled 
into  action  fimilar  to  the  vital  one.  But  if  the  com- 
preffion  be  removed  from  the  nerve,  the  mufcle  re- 
covers the  power  by  which  it  is  put  into  action. 
When  the  nerve  is  irritated  below  the  place  where 
it  is  cut,  the  mufcle  to  which  that  nerve  belongs  is 
contracted.  Numerous  experiments  liave  been  made, 
to  prove  this,  efpsdally  on  the  phrenic  and  recur- 
rent nerves. 

cccciv.  This  power  is  not  the  fame  with  the  vis 
infita.  The  former  is  adventitious  to  the  mufcle  ; 
whereas  the  latter  is  inherent  in  it.  The  tnrmer 

ceafes 


Chap.  XL  MUSCULAR  MOTION. 


193 

ceafes  along  with  life  whereas  the  latter,  accord^ 
ing  to  certain  experiments,  fubfifts  long  after  it. 
Th^e  former  is  fupprexTed-,  by  tying  a ligature  upon 
the  nerve,  by  injuring  the  brain,  or  by  the  exhibi- 
tion of  opium.  The  latter  is  not  affeded  by  thefe 
circumftances,  but  continues  after  the  nerve  is  tied 
or  cut,  and  even  in  the  intehines,  though  taken  out 
of  the  body ; it  alfo  exiils  in  animals  deftitute  of 
brain  : parts  of  the  body  poffefs  motion,  which  are 
deftitute  of  fenfation,  while  others  poffefs  fenfation ^ 
which  are  deftitute  of  motion.  The  will  excites 
and  removes  the  nervous  action,  but  has  no  power 
over  the  vis  inftta. 

ccccv.  In  mufcular  action,  whether  proceeding 
from  the  vis  inftta,  or  from  the  nervous  power,  the 
fibres  are  contraded  towards  the  middle  of  its 
belly,  and  expand  outwards : they  are  varied  by 
tranfverfe  wrinkles,  and  the  whole  mufcle  becomes 
fliorter,  and  draws  its  extremities  towards  its 
centre,  and  therefore  carries  tow'ards  each  other 
thofe  parts  with  which  ' it  is  conneded,  in  the  re- 
ciprocal proportion  of  their  firmnefs.  Mufcles,  dur- 
ing their  contradion,  fwell,  and  at  the  fame  time 
become  hard,  and,  as  it  were,  increafe  their  cir-* 
cumference  every  where.  I have  never  obferved 
them  to  turn  pale.  Whether,  on  the  whole,  they 
are  increafed  in  bulk,  and  acquire  more  in  breadth 
than  they  lofe  in  length,  is  difficult  to  be  known. 
They  draw  after  them  the  paffive  tendons,  which 
of  themfelves  are  neither  moveable  or  irritable. 
The  whole  of  a mufcle  may  be  moved  at  once,  or 
only  a part  of  it : if  one  extremity  is  ftxed  to  an 
immoveable  part,  that  only  is  moved,  which  is  ca- 
pable of  yielding. 

ccccvi.  Do  the  arteries  contribute  in  anyway  to 
mufcular  motion,  as  indicated  by  the  paralyfts  of  the 
lower  extremities,  produced  by  tying  the  aorta? 
Not  at  all,  unlefs  by  prefer ving  the  integrity  of  the 
mufcles,  and  mutual  relation  of  the  parts,  by  fecret- 
ing  vapour  and  fat,  aijd  by  ngurilhing  them.  For 
Q , by 


MUSCULAR  MOTION.  Chap.  II. 


194 

by  dividing  or  tying  its  art9,r)%  a mufcle  does  not 
become  paralyfed,  unlefs  aftbr  a conLderable  time, 
when  the  mufcles  begin  to  be  dellroyed  by  gan- 
grene. The  irritation  of  the  artery  has  no  effect 
on  the  mufcles.  Moreover,  it  is  impracticabie  to 
explain  the  motion  of  peculiar  mufcles  from  a caufe, 
which,  proceeding  from  the  heart,  operates  with 
equal  force  on  all  parts  of  the  body.  Laftly,  the  in- 
iiuence  of  the  will  is  confined  to  the  nerves,  and 
does  not  extend  to  the  arteries  or  other  folid  parts 
of  the  body. 

ccccvii.  But  the  manner  in  which  the  nerves 
excite  motion  in  the  mufcles,  is  fo  obfeure,  that  we 
may  aim.off  defpair  of  difeovering  it.  And  we  do 
not  even  attempt  to  inveftigate  the  vis  infita,  which 
feems  to  be  an  increafed  attraction  of  the  elementa- 
ry parts  of  the  fibre,  by  which  they  mutually  ap- 
proach each  other,  and  accumulate  contortions  in 
the  middle  of  the  fibre.  This  force  of  attraction, 
which  is  implanted  by  nature  in  the  mo^'ing  fibre, 
is  excited  and  increafed  by  ftimuli.  The  reft  is 
mere  hypothefis.  As  to  nervous  vcficles  fwelling 
by  a quicker  infiux  of  the  nervous  fluid,  they  are 
inconfiftent  with  anatomical  truth,  which  demon- 
flrates  the  fibres  to  be  cylindrical,  and  in  no  part 
veficular  ; and  likewife  with  the  celerity  with  wlrich 
mufcular  mmtion  is  perform.ed,  and  with  the  bulk 
of  a mufcle  being  rather  diminiflred  than  increafed 
during  its  action.  The  chains  and  rhombs  of  the 
inflated  fibres  are  in  the  fame  manner  repugnant 
to  anatomical  infpection,  and  to  the  celerity  ; they 
Vvmuld  alfo  occafion  an  immenfe  wafle  of  power, 
and  render  the  mufcle  but  little  fhorter.  The 
nerves  want  that  irritable  nature  which  is  obferved 
in  the  mufcular  fibre ; and  befides,  it  is  by  no  means 
demonftrable,  that  the  fibres,  fo  numerous,  can  arife 
from  nerves,  fo  few  and  diffributed  in  a different 
direction,  almoffti'anfverfelywith  refpeetto  the  muf- 
cular fibres.  The  idea  of  nerves  being  difpofed  round 

arterial 


Chap.  XI.  MUSCULAR  MOTION. 


195 

arterial  fibres,  compreffing  them  by  their  elafticity, 
is  founded  upon  a falfe  ftruflure  of  the  fibre,  which 
is  gratuitoufly  aflumed  to  be  filled  with  blood,  and 
fuppofes  nerves,  where  cellular  fibres  only  can  be 
demonftrated.  Moreover,  the  phenomena  of  ani- 
hials,  which  have  neither  brain  or  nerves,  and  ai'e 
yet  very  capable  of  motion,  demonftrate  the  fabric 
of  the  mufcles  to  be  fufficient  for  their  motion,  even 
without  nerves.  Blood  globules,  filled  with  air,  and 
the  explanations  derived  therefrom,  fuppofe  a falfe 
nature  of  that  fluid ; namely,  that  elaftic  air  exifts, 
where  it  does  not  (cclxXxi.)  The  animal  fpirits 
are  not  of  the  nature  of  eledlricity. 

ccccviii.  If  we  may  add  any  thing  to  the  phe- 
nomena, we  may  fuppofe  the  nervous  liquor  to  be 
of  a ftimulating  nature,  forcing  the  elementary  par- 
ticles of  the  mufcular  fibre  to  approach  nearer  to 
each  other.  The  motive  caufe  which  occafions  the 
influx  of  the  fpirits  into  the  mufcle,  fo  as  to  excite 
it  into  adfion,  feems  not  to  be  the  foul,  but  a law 
eftablifhed  by  the  Creator.  For  animals,  newly 
born,  or  newly  transformed,  without  any  attempt, 
or  exercife,  know  how  to  perform  compound  mo- 
tions, very  difficult  to  be  defined  by  calculation. 
But  the  foul  learns  thofe  things,  which  it  performs, 
flowly,  imperfectly,  and  experimentally.  Mufcles, 
therefore,  contraft,  which  in  a given  time  receive 
more  of  the  nervous  fluid,  whether  that  be  occa- 
fioned  by  the  will,  or  by  fome  irritating  caufe  arif- 
ing  in  the  brain,  or  applied  to  the  nerve. 

ccccix.  Though  the  foul  may  be  fuppofed  to  adt 
in  nervous  motions,  it  cannot  be  admitted  in  thofe 
arifing  from  the  vis  infita.  The  heart  and  intef- 
tines,  alfo  fome  organs  of  the  venereal  appetite,  are 
governed  by  the  vis  infita,  and  by  ftimuli.  Thefe 
powers  do  not  arife  from  the  will ; nor  are  they  lefl- 
ened,  or  excited,  or  fupprefled,  or  changed  by  it. 
No  cuftom  or  art  can  fubjedf  thefe  organs  of  inhe- 
rent motion  to  the  will,  or  caufe  a fateliitc  of  vbl- 
0 4 untary 


MUSCULAR  MOTION.  Chap.  XL 


tg6  ■ 

Hntary  motion  to  forget  to  obey  the  commands  of 
the  foul.  It  is  fo  certain,  that  motion  is  produced 
by  tlie  body  alone,  that  we  cannot  even  fufpsct  any 
motion  to  arife  from  a fpiritual  caufe,  except  that 
which  the  will  feems  to  excite  in  animals  ; and, 
even  in  the  very  organs  of  animal  volition,  a ftim- 
ulus  will  accafion  the  mofc  excellive  aCdons,  in  di- 
recL  oppofition  to  the  will. 

cccGx.  There  feems  to  be  this  difference  between 
the  mufcles  obeying  the  will,  and  thofe  which  are 
govei’ned  by  the  vis  infita,  that  the  latter  are  more 
irritable,  and  are  very  eafily  excited  into  action  by 
a gentle  flimulus  ; as,  for  inftance,  the  heart  and 
inteftines  ; \ehich  organs  are  moft  manifeflly,  and 
greatly,  and  Gonhantly,  irritable.  On  the  other 
hand,  the  mufcles  which  obey  the  will,  are  Icfs  ea- 
lily,  and  lefs  durably  irritable.  Hence,  they  either 
need  the  agency  of  the  will,  or  of  a powerful  ftim- 
ulus  ; by  which,  indeed,  even  tliefe  may  be  excited 
to  action,  independent  of  the'wiU.  Thus,  it  hap- 
pens, that,  in  apoplexy,  the  mufcles  which  obey  the 
will,  being  deprived  of  all  influx  from  the  brain, 
lang'uifh,  and  become  paralytic  ; while  the  vital 
mufcles,  having  no  occafion  for  the  operation  of 
the  brain,  continue  to  be  excited  into  contraction 
by  their  Itimivli ; the  heart  by  the  blood,  and  the 
inteftines  by  the  air  and  aliments. 

ccccxh  The  ftrength  of  this  action  is  very  con- 
ficlerable  in  all  perfons,  but  more  efpecially  in  mad- 
men, and  in  feme  ftrong  men  ; fince  frequently, 
with  a few  mufcles  only,  they  wall  raife  a weight, 
much  greater  than  that  of  the  whole  human  body. 
But  even  in  healthy  people,  very  flender  mufcles 
have  elevated  2co  or  300  pounds.  The  mufcles  of 
the  back  will  even  fuftain  3000.  Notwithflanding 
this,  much  the  greater  part  of  the  force  or  power 
exerted  by  a mufcle,  is  always  loft,  without  produ- 
cing any  vifible  effect.  For  aU  mufcles  are  inferted 
nearer  the  fulcrum,  than  the  weights  are  append- 


Chap.  XL  MUSCULAR  MOTION. 


19.7 

cd  ; and  therefore  their  action  is  lellened.  In  pro- 
portion as  their  lever  is  Ihorter  than  that  of  the 
weight.  Moreover,  moft  of  the  mufcles  are  infert- 
ed  into  the  bones,  elpecially  in  the  limbs,  at  very 
acute  angles ; whence,  again,  the  eflFed;  which  a 
mufcle  exerts  in  aftion,  is  proportionably  lefs  than 
the  effort  which  it  exerts,  as  the  fine  of  the  angle 
intercepted  betwixt  the  bone  and  the  mufcle,  is  lefs 
than  the  whole  fine.  Again,  the  half  of  every 
mufcular  effort  is  loft,  becaufe  it  may  be  confidered 
as  an  elevating  cord,  drawing  an  oppoftte  weight 
to  its  fixed  point.  Beftdes,  many  of  the  mufcles 
are  feated  in  the  angle  between  two  bones,  arifing 
from  the  one,  and  moving  the  other  ; and  therefore, 
on  that  bone  being  moved,  they  are  bent,  and,  like 
inflefted  cords,  require  a new  force  to  extend 
them.  Many  of  them  pafs  over  feveral  joints,  each, 
of  which  they  bend  in  feme  degree,  fo  that  only  a 
fmall  part  of  their  effort  remains  to  bend  their  prop- 
er joint.  The  fiefhy  fibres  themfelves  of  the  muf- 
cles very  often  form  angles  with  their  common 
tendon,  whence  a great  part  of  their  force  is  again 
loft,  and  only  that  proportion  cf  the  whole  remains,- 
which  is  as  the  line  of  the  angle  of  their  infertion 
to  the  whole.  Tinaily,  the  mufcles  move  their  op- 
pofed  weights  with  very  great  velocity  and  eafe,  fo 
that  they  not  only  overcome  the  equilibrium,  but 
likewife  add  a confiderable  excefs  of  velocity; 

ccccxii.  Allthefe  Ioffes  of  power  being  compu- 
ted, make  it  evident,  that  the  force  exerted  by 
mufcles  in  aftion,  is  exceedingly  great,  and  totally 
different  from  any  mechanical  proportion  ; fince 
the  effecl  is  fcarce  -go  of  the  whole  force  exerted 
by  the  mufcle,  and  yet  a few  mufcles,  weighing 
but  a few  pounds,  are  able  not  only  to  raife  fome 
thoufands  cf  pounds,  but  aifo  with  very  great  ve- 
locity. Nor  is  this  to  be  reputed  any  defefl:  of 
wifdom  in  the  Creator  : for  all  thefe  lofl'es  of 
power  were  rendered  neceflary,  on  account  of  the 

fymmetry 


MUSCULAR  MOTION.  Chap.  XL 


198 

fymmetry  of  the  body,  of  mufcular  motion,  and  of 
the  requifite  celerity  and  direction  ; whereas  the 
contrary  of  all  thefe  is  required  in  the  mechanifm 
of  machinery.  We  may,  however,  certainly  con- 
clude from  hence,  that  the  action  of  animal  motion 
is  very  powerful,  fince,  in  a fmall  organ,  it  can 
exert  a force  equal  to  fome  thoufand  pounds  for  a 
conliderable  time,  or  even  for  entire  days  ; nor  does 
this  feem  to  be  otherwife  explicable,  than  by  the 
incredible  celerity  with  which  the  influx  of  this  fluid 
obeys  the  command  of  the  wiU.  But  from  whence 
this  velocity  proceeds,  we  are  unable  to  fay,  and 
muft  rell  fatislied  with  knotting  that  there  exifts  a 
law,  by  which,  at  a given  volition,  a given  celerity 
is  produced  anew  in  the  nervous  fluid. 

ccccxiii.  The  equilibration  of  imifcular  motion 
is  aflifted  by  the  action  of  antagonift  powers. 
Namely,  in  all  parts  of  the  human  body  evcry 
inufcle  is  counterpoifed  by  fome  counteracting 
weight,  or  by  elafticity,  or  by  mufcles,  or  by 
a fluid  which  reacts  upon  hollow  mufcles,  by 
which  it  is  expelled,  This  caufe  is  the  vis  infita, 
and  operates  continually,  even  vchile  the  mufcle 
adts  ; and  fo  foon  as  the  additional  celerity  derived 
from  the  brain  remits,  its  aftion  reftores  the  limb 
or  other  part  immediately  to  its  former  Rate,  in 
which  tliere  is  an  equilbrium  betwixt  the  mufcle 
and  its  oppofing  caufe.  Whenever  mufcles  confli- 
tute  the  antagonift  power,  none  of  them  can  con- 
tract without  extending  their  antagonifts,  by  which 
the  nerves  being  diftended,  and  a fenfe  of  uneafl- 
nefs  produced,  a ftill  ftronger  endeavour  towards 
reftoring  the  equilibrium  is  excited.  Hence,  when 
a flex  or  mufcle  is  divided,  the  extenfor  operates 
even  in  the  dead  body  ; and  the  reverfe. 

ccccxiv.  But  there  are  acceflbry  means,  by  which 
the  motions  of  the  mufcles  are  rendered  fafe,  cer- 
tain and  -eafy.  The  large  long  mufcles,  by  which 
the  greater  flexions  are  performed,  are  included  in 

firm 


Chap.  XI.  MUSCULAR  MOTION. 


199 


firm  tendinous  Iheaths,  which  are  drawn  and  tight- 
ened by  other  mufcles  ; for  thus,  while  the  joint 
is  bent,  the  mufcle,  though  in  a ftate  of  contraction, 
remains  preiied  againft  the  bone,  and  a confiderable 
lofs  of  power  is  avoided.  But  the  long  tendons, 
which  are  incurvated  or  extended  over  joints  which 
are  bent  when  they  are  moved,  are  received  with- 
in proper  braces,  which  have  lubricated  canals  hol- 
lowed out  in  them,  and  which,  at  the  fame  time 
that  they  do  not  interrupt  their  motion,  keep  the 
tendons  fteady,  fo  that  they  neither  can  be  difplac- 
ed,  nor  get  rigid  under  the  Ikin,  with  pain  and 
lofs  of  motion.  In  thefe  tubular  braces,  a proper 
liniment  is  poured  around  the  tendons.  The  fame 
oiEce  is  performed  in  Tome  lituations  by  perforated 
-mufcles  themfelves.  In  other  parts,  the  tendons 
are  either  carried  round  eminences  of  bone,  in  or- 
der that  they  may  be  inferted  at  greater  angles 
into  the  bone  which  they  move  ; or  they  are  in- 
ferted into  another  bone,  from  whence  a different 
tendon  defcends  under  a much  larger  angle  into 
the  bone  to  be  moved.  In  other  parts,  nature  has 
carried  the  mufcles  derived  from  convenient  litua- 
tions,  in  a contrary  direclion  into  the  part  to  be 
moved,  as  it  were  round  a pully.  She  has  likewifc 
furrounded  the  mufcles  on  all  lides  with  lubrica- 
ting fat,  both  the  fibrils,  fibres,  lacerti  and  mufcles  ; 
which  fat,  being  compreffed  and  effufed  amongfl; 
the  tumid  mufcles  and  fibres,  anoints  the  fibres, 
and  prefcrves  their  flexibility. 

ccccxvi.  Moreover,  the  effeiT  of  one  mufcle  is 
determined  by  the  co-operation  or  oppofltion  of 
others,  which  either  hold  firm  the  part  from  which 
the  mufcle  arifes,  or  bend  it,  or  elfe,  by  the  concur- 
rence of  their  action,  change  the  action  of  the 
mufcle  from  its  flraight  courfe  to  its  diagonal, 
Mufcles  alfo  affift  each  other,  even  though  fituated 
at  a confiderable  diftance,  by  the  one  keeping  the 
bone  fteady,  out  of  wlijch  the  other  arifes.  There- 
fore, 


soo 


MUSCULAR  MOTION.  Chap.  XL. 


fore,  the  aclion  of  no  mv.fcle  can  be  underftood 
from  confidering  it  alone ; but  all  the  others  muft 
likewife  be  confidered  at  the  fame  time,  which  are 
either  inferted  into  the  rnufcle  itfelf,  or  into  any 
of  the  parts  to  which  the  faid  rnufcle  adheres. 

ccccxAHi.  By  thefe  mufcles  varioufly  confpiring 
and  oppofing  each  other,  are  performed  walking, 
handing,  flexion,  extenfion,  deglutition,  and  all  the 
other  functions  of  human  life.  But  the  actions  of 
the  mufcles  are  alfo  generally  ufeful.  They  ac- 
celerate the  return  of  the  venous  blood,  by  com- 
prciiing  both  the  contiguous  veins  between  the  tu- 
mid mufcles,  and  the  veins  proper  to  the  mufcles 
between  their  turgid  lacerti,  and  by  the  force  of  that 
preffure  being  determined  by  the  valves  towards  the 
heart  only,  they  afilfc  the  powers  of  the  heart : they 
likewife  return  the  fat  to  the  blood  ; and  agitate, 
and  triturate  the  arterial  blood,  and  fupply  it  more 
quickly  to  the  lungs.  They  influence  the  fecretions 
and  excretions,  retarding  or  accelerating  them  ; 
in  the  liver,  mefentery,  womb,  &c.  they  promote 
the  courfe  of  tlie  contained  blood,  bile,  and  other 
juices,  and  Icffen  the  danger  of  their  flagnation  : 
they  increafe  the  flrength  of  the  ftomach,  by  the 
addition  of  their  own,  whereby  digeftion  is  pro- 
moted ; infomuch  that  aU  fcdentary  and  inactive 
courfes  of  life  are  contrary  to  the  appointment  of 
nature,  and  predifpofe  to  difeafcs  arifing  from  ftag- 
nation  of  the  fluids,  and  crudity  of  the  aliaments. 
The  large  mufcles,  which  are  placed  round  the 
belly,  propel  the  blood  contained  in  that  cavity, 
and  prefs  it  towards  the  heart.  But  by  mucii  ac- 
tion, the  inufcles  themfelves  become  indurated  and 
tendinous,  and  they  convert  the  cartilaginous  and 
membranous  parts  upon  which  they  are  incumbent, 
into  a bony  nature  ; they  increafe  the  inequalities 
and  procefles  of  the  bones,  and  excavate  the  fides 
contiguous  to  them  j they  obliterate  the  cells  feat- 


Chap.  XII, 


TOUCH. 


20J 


ed  in  the  diploe,  and  bend  the  bones  towards  them-, 
felves. 

ccccxviii.  Mufcles  which  are  not  excited  by  a 
ftimulus,  or  for  which  the  mind  has  no  occafion, 
become  relaxed  and  foft ; their  wrinides  are  fmooth- 
ed  out,  their  fibres  are  rendered  longer,  receding 
from  the  middle  towards  the  fixed  extremities  ; 
and  the  whole  mufcle  collapfes  the  accefibry  caufe 
of  contradion,  whatever  it  is,  is  removed  ; while 
that  remains  without  which  the  mufcle  never  is,  as 
long  as  it  is  alive.  Nor  is  there  any  occafion  for 
antagonifl;  mufcles,  although  they  may  afiift.  It  has 
been  alked.  What  becomies  of  the  fpirit  that  is  fent 
from  the  brain  ? A part  of  it  perhaps  is  exhaled  ; 
I fufped'a  part  to  adhere  to  the  fibre;  and  that 
this  is  the  reafon,  that  by  exercife  the  mmfcles  grow 
ftronger,  and  the  limbs  become  thicker. 


ecccxix.  HE  other  office  of  the  nerves  and 


fer  changes  from  the  impreflions  of  external  fub-. 
fiances  in  the  parts  of  the  body  affected  by  them, 
and  to  undergo  analagous  changes  in  the  reprefem 
tations  in  the  mind.  We  lhall,  therefore,  firft  ex- 
amine each  of  the  fenfes  in  particular  ; and  then 
confider  what  is  common  to  all  of  them,  and  what 
happens  in  the  mind  from  the  changes  in  the  or- 
gans of  fenfe. 

ccccxx.  Touch  is  underftood  in  a twofold  man- 
ner. For,  by  this  term,  in  general,  we  call  every 
change  of  the  nerves,  arifing  from  heat,  cold, 
roughnefs,  fmoothnefs,  weight,  moifture,  or  drynefs 
in  external  bodies,  in  whatever  part  of  the  body  that 
change  may  arife.  In  this  acgeptation,  touch  is  afi 


CHAP.  XII, 


TOUCH, 


brain  is  fenfation ; that  is,  to  fuf- 


402 


TOUCH. 


Chap.  XII. 


cribed  to  almoft  all  parts  of  the  human  body,  in 
a greater  or  lefs  degree  ; as  in  different  places  of 
the  body  the  nerves  are  more  numerous,  bare,  or 
covered  with  thinner  membranes  , and  in  this  fenfe 
pain,  pleafure,  hunger,  thirft,  anxiety,  itching, 
and  the  other  fenfations,  belong  to  the  fenfe  of 
touch. 

ccccxxi.  But,  in  a fomewhat  different  and  more 
proper  acceptation,  the  feiife  of  touch  is  faid  to  be 
the  change  from  external  bodies  which  is  produ- 
ced in  the  fkin,  more  efpecially  at  the  ends  of  the 
fingers,  and  is  rcprefented  to  the  mind.  For,  by 
the  fingers,  we  mofl  accurately  difUnguiffi  the  tan- 
gible qualities  of  bodies, 

ccccxxii.  Indeed,  in  the  fkin  we  do  not  eafily 
diftingulfli  any  particle  which  does  not  feel.  But 
fince  the  touch  is  commonly  afcribcd  in  a peculiar 
manner  to  the  papillse,  the  ftructure  of  the  fkin 
muft  be  defcribed.  What  is  ftrictly  called  the 
fldn,  is  compofed  of  a denfe  web  of  very  compact 
cellular  fubflance,  whofe  fibres  are  intermixed  and 
interwoven,  which  renders  it  highly  extenfible,  con- 
tractile, and  porous.  Its  ftrata,  which  are  expof- 
ed  to  the  air,  and  next  to  the  epidermis,  are  more 
clofely  compacted  ; as  they  approach  the  fat,  they 
are  gradually  relaxed,  and  refolved  into  a fofter  cel- 
lular texture.  It  is  more  tender  in  fome  places, 
and  in  others  firmer.  It  is  pervaded  by  many  fmall 
arteries,  which  come  from  the  fubcutaneous  ones  : 
they  are  neither  large  nor  long,  but  are  numerous 
in  forne  parts  where  the  fkin  is  red,  as  in  the 
cheeks  ; in  other  parts  they  are  fewer  in  number, 
d’he  veins  arife  in  great  numbers  from  the  fubcu- 
taneous reticulations  : the  nerves  likewife  in  the  fkin 
are  very  numerous ; but  they  vanifir  fo  fuddenly, 
that  it  is  very  difhcult  to  trace  their  ultimate  ex- 
tremities. Betwixt  the  fkin  and  mufcles,  there  is 
cellular  fubflance,  into  which  the  fkin  infenfibly 
refolved,  degenerates,^  in  mofl,  parts  repieniflied 

witii 


Chap.  XII. 


TOUCH. 


203 


with  fat,  of  which  the  little  eminences  form  pits 
in  the  Ikin  ; but  in  fome  parts,  as  the  penis,  red 
part  of  the  lips,  &c.  it  is  deftitute  of  fat.  There 
are  very  few  parts  in  the  human  body  where  muf- 
cular  fibres  are  immediately  contiguous  to  the  Ikin, 
without  any  feparation  by  fat ; for  the  dartos  is 
only  cellular  fubftance,  and  has  no  mufcular  fibres. 
There  are  fome  places  where  tendinous  fibres  are 
inferred  into  the  fein  ; as  in  the  palms  of  the  hands, 
and  foies  of  the  feet. 

ccccxxiii.  Throughout  the  Ikin  in  general,  in 
mofi:  parts  of  the  body  of  man  or  of  the  larger  ani- 
mals, on  removing  the  epidermis,  fcarcely  an  une- 
vennefs  is  perceptible,  unlefs  very  minute  granula- 
tions, raifed  hardly  any  vifible  height,  and  obtufe. 
But  in  the  ends  of  the  fingers,  papillae,  fomewhat 
larger,  but  Hill  very  difficult  of  demonllration  to 
the  fight,  are  feated  in  cavities  of  the  cuticle,  and 
receive  nerves  fcarcely  vifible ; they  are  minute 
projeftions,  formed  of  velfels  with  one  or  more 
linall  nerves,  wrapped  up  in  cellular  fubftance. 
In  the  lips,  after  maceration,  they  appear  long  and 
villous ; in  the  penis  they  are  flaky  ; and  in  the 
tongue  they  are  moll  evident,  from  the  fabric  of 
which  we  conclude,  by  analogy,  with  refpecl  to 
the  other  cutaneous  papillae. 

ccccxxiv.  The  Ikin  is  furrounded  by  another 
covering,  which  refills  completely  the  adlion  of  the 
air,  and  which  coheres  with  the  Ikin  by  an  infi- 
nite numiber  of  frnall  veffels,  and  by  hairs  palling 
through  it.  The  outer  furface  of  this  covering, 
of  a corneous  nature,  dry,  infenlible,  not  fubje<T  to 
putrefadlion,  dellitute  of  veflels  and  nerves,  wrink- 
led in  a particular  manner,  and  reticular  towards 
the  Ikin,  is  called  the  epidermis.  It  is  perforated 
by  an  infinite  number  of  pores,  of  which  the  larger 
ones  are  perfpirative,  and  the  fmaUer  vaporiferous, 
and  is  connedled  with  the  Ikin  by  numerous  mi- 
nute vefl'els  refembling  down.  By  preflure  or  burn- 
ing, 


204 


TOUCH. 


Ci-iAr.  XIL 


ing,  the  cutkle  grows  thicker,  by  the  addition  o£ 
new  plates,  formed  between  it  and  the  fs:in  ; and  is 
then  faid  to  be  callous.  But  even  without  difeafe, 
in  negroes  the  two  plates  are  diftincc. 

ccccxxv.  The  inner  furface  of  the  cuticle,  more 
foft,  pulpy,  half  fluid,  refembling  concreted  mucus,, 
is  feparated  with  dilliculty  in  Europeans,  but  eafily 
in  the  African  negro,  in  whom  it  is  truly  mem-, 
branaceous,  folia,  and  feparable  ; and  in  the  palate 
of  brutes.  It  is  incumbent  on  the  lldn,  of  v Inch 
it  receives  the  papillae  into  foft  pits.  It  is  called 
the  rete  Malpighianum,  although  it  be  certain  that 
it  is  not  perforated  in  a confpicuous  manner,  as  a 
lieve. 

ccccxxvi.  That  this  reticular  body  is  compofed 
by  the  concretion  of  fome  fluid,  tranfuding  from 
the  fldn,  feems  very  probable.  The  fabric  of  the 
cuticle  is  ftiil  uncertain  ; for  fince  it  is  defiitute  of 
veffels,  is  regenerated,  and  is  infeniible,  it  does  not 
feem  to  belong  to  the  organical  parts  of  the  body. 
Is  it  the  outer  part  of  the  Malpighian  mucus 
(ccccxxv.)  coagulated  and  conclenfed  by  the  air 
and  by  prefllire  ; which  is  perforated  in  many 
places  by  exhaling  and  inhaling  ducts,  the  mouths 
of  which  are  cemented  together  by  the  interpofed 
condenfed  glue  ? Is  this  opinion  fupported  by  the 
mucous  expanfion  upon  the  membrane  of  the  tym- 
panum j by  its  diffolution  in  water,  as  obfervxd  by 
eminent  anatomills,  though  by  others  denied,  in 
.the  cuticle  of  negroes  ? 

ccccxxvii.  Moreover,  to  the  hiftory  of  the  fkin 
belong  the  firaple  glands,  which  are  feated  in  very 
•many  places  under  the  fkin  in  the  cellular  fub- 
■llance,  and  perforate  it  by  their  excretory  ducts, 
and  pour  out  upon  the  cuticle,  in  the  hair)’  fcalp, 
and  in  the  convex  furface  of  the  ear,  a fat  foft 
half  fluid  liniment.  Other  febaceous  glands,  partly 
fimple,  and  partly  compound,  generate  in  the  face, 
though  more  fiO'.vly,  a dry  vdiite  liniment,  but  in 


Chap.  XU. 


TOUCH. 


so5 


the  groins  and  armpits  one  more  oily,  with  which 
the  &in  being  anointed,  Ihines,  and  is  defended  both 
from  the  air  and  from  friftion.  They  are  found  in 
all  parts  of  the  human  body  tha.t  are  under  the  ne- 
ceffity  of  being  more  immediately  expofed  to  the 
air,  as  in  the  face,  where  there  are  a great  number 
of  the  compound  fort ; or  wherever  the  Ikin  is  li- 
able to  great  friclion,  as  in  the  breails,  armpits, 
groins,  glans  penis,  nymphae,  anus  and  hams.  They 
frequently  fend  out  hairs.  Are  follicles  of  this  kind 
feated  -in  all  parts  of  the  fkin  ? Although  anatomy 
does  not  demonftrate  them,  yet  it  feems  probable 
that  they  are  prefent  every  where,  as  appears  from 
the  fordes,  coUecled  about  the  whole  furface  of  the 
body,  feemingiy  of  the  febaceous  kind.  But  anoth- 
er fort  of  oily  ointment  (ccix.)  is  pOured  out  up- 
on the  Ikin,  through  its  pores,  from  the  fat  itfeif, 
without  the  intervention  of  glands,  efpecially  where 
the  Ikin  is  clothed  with  hair, 

ccccxxviii.  The  hair  and  nails  are  alfo  appen- 
dages to  the  Ikin.  The  former  are  icattered  over 
aimoft  the  whole  furface  of  the  body,  the  palms  of 
the  hands  and  foies  of  the  feet  excepted  ; in  moft 
parts  fiiort  and  foft ; but  longer  upon  the  Ikin  of 
the  head,  cheek,  chin,  and  break  in  men  ; alfo,  up- 
on the  forepart  of  the  limbs,  in  the  armpits,  groins, 
and  pubis.  They  arife  from  the  fubcutaneous  cel- 
lular fubkance,  originating  from  a little  bulb,  which 
is  membranous,  krong,  vafcular,  of  an  oval  fhape, 
and  more  lax  towards  the  cellular  texture,  at  which 
part  it  is  alfo  furnifhed  with  vekels  ; in  which  little 
bulb  another  bulb  lies  hid,  roundiki  at  its  begin- 
ning, but  afterwards  cylindrical,  and  furrounded 
v/ith  blood.  In  this  fecond  bulb  lies  the  hair,  cov- 
ered with  a fatty  humour.  The  hair,  with  both  its 
cylindrical  Iheaths,  arrives  at  a cutaneous  pore,  goes 
out  through  it, and  forces  the  epidermis  into  afimilar 
flieath  ; whence  the  very  great  kability  of  the  hair  : 
after  this  the  iheath  cannot  be  any  longer  feparated 

from 


2o6 


TOUCH. 


Chap.  XIL 


from  the  cortex  ; the  filaments,  and  fpongy  and 
cellular  matter,  are  continued  throughout  the  whole 
length  of  the  hair.  The  hairs  grow  naturally  in 
the  fubcutaneous  cellular  fubftance;  but,by  difeafe, 
they  are  fometimes  formed  in  other  fituations  with- 
in the  fat.  They  grow  continually ; and  when  cut, 
are  renewed  by  the  protrulion  of  their  medullary 
fubftance  from  the  fkin  outwardly,  and  by  the  pro- 
longation of  the  cuticle.  In  old  age,  the  hairs,  def- 
titute  of  this  medulla,  dry  up,  fplit,  and  fall  off. 
Their  colour  is  from  the  juice,  which  fills  the  inter- ' 
nal  cellular  texture.  They  feem  to  exhale  through 
their  extremities,  and  pofiibly  throughout  their 
whole  furface,  as  we  may  conclude  from  the  con- 
ftant  protrufion  of  their  medulla,  which  ought  to 
have  an  end  from  the  plica  Polonica,  and  from  the 
luminous  rays  that  come  out  from  .the  hairs  of  an 
animal  elecfrified.  The  fubcutaneous  fat  follows  the 
courfe  of  the  hairs,  and  is  exhaled. 

ccccxxix.  The  nails  are  of  the  nature  and  fabric 
of  the  cuticle,  and  fall  off  along  with  it,  being  in 
like  manner  infenfible,  and  capable  of  reproduc- 
tion. They  are  found  upon  the  end  of  the  fingers 
and  toes,  occupying  their  upper  and  back  part, 
and  correfpond  to  the  tactile  papillary  apex,  which 
they  fupport,  and  retain  applied  to  the  object  felt. 
They  arife  from  a fquare  root,  between  an  inter- 
nal ftratum  of  the  fldn,  mixed  with  periofteum, 
and  another  external  ftratum,  a little  beyond  the 
laft  articulation  : they  go  out  by  a lunar  cleft  in  the 
external  plate  of  the  fkin,  where  the  cuticle  partly 
returns  back  towards  the  root  of  the  nail,  to  which 
it  adheres,  and  is  partly  laid  over  the  outfide  of 
the  nail,  and  extended  forward  vith  it,  forming  its 
outer  covering.  The  nail  itfelf  is  foft  when  it  is 
firft  produced,  and  in  the  part  covered  by  the 
fkin  ; but,  by  age,  and  contacl;  with  the  air,  it  be- 
comes harder,  corneous,  folid,  and  elaftic,  compofed 
of  long  fibres  cemented  by  gluten,  feparated  by 

fulci. 


Chap.  XIL  TOUCH.  207 

fulci,  fiiiile,  and  of  many  layers.  The  nail  thus 
formed,  extends  itfelf  to  the  extremity  of  the  lin- 
ger ; and,  through  its  whole  extent,  its  inlernal 
ftriated  furface  is  lined  by  furrowed  Ikin,  blended 
with  periofteum,  of  which  the  filaments  are  hrli; 
fliort,  afterwards  longer,  and  thofe  which  adhere 
near  the  point  of  the  nail  are  the  longeft  of  ail. 
Thefe  are  moft  intimately  connected  with  the  root 
of  the  nail.  Beyond  the  adhering  part  of  the  nail, 
the  fldn  asrain  becomes  free  and  unconneded  with 

O 

the  nail,  and  has  its  own  epidermis.  A furrowed 
network  is  interpofed  betwixt  the  lldn  and  nail, 
which  is  feparabie  and  foft,  for  the  protection  of 
the  papillae  ; where  the  furrows  are,  it  becomes 
gradually  harder,  fo  that  at  laft  it  can  fcarcely  be 
diflinguifhed  from  the  nail.  The  tendons  do  no^ 
reach  fo  far  as  the  nail. 

ccccxxx.  The  fubcutaneous  cellular  fubfcance  in 
very  few  places  is  without  fat,  on  account  of  the 
neceffary  motion  of  the  fkin.  Wliere  it  is  replen- 
iflied  with  fat,  it  defends  the  warmth  of  the  internal 
parts  from  the  air  ; it  renders  the  Ikin  moveable 
upon  the  mufcles  ; it  fills  up  the  cavities  between 
the  mufcles  themfelves  ; and  contributes  to  the 
W'hitenefs  and  beauty  of  the  body.  The  fkin,  Mal- 
pighian mucus  and  cuticle,  not  only  cover  the  exter- 
nal furface  of  the  body  every  where,  but  likewife, 
where  they  feem  to  be  perforated,  returning  inwards 
they  gradually  change  their  appearance.  For  the 
cuticle  is  manifeft  in  the  anus,  urethra,  vagina,  cor- 
nea of  the  eye,  auditory  paffage,  mouth  and  tongue ; 
nor  is  it  wanting  even  in  the  ftomach  itfelf  and  in- 
teftines  j although,  by  the  perpetual  emoliition,  its- 
fabric  be  altered,  and  relaxed  into  their  villous 
coat.  Thus  the  true  fkin,  being  continuous  with 
the  internal  fabric  of  the  palate,  tongue,  pharynx, 
noftrils,  vagina,  &c.  changes  every  where  into  the 
wlute,  thick,  pulpy,  commonly  called  nervous,  coat 
of  thofe  parts. 


ccccxxxi. 


2o8 


TOUCH. 


Chap.  XII. 


ccccxxxi.  What  has  been  hitherto  advanced,  is 
fufficient  to  enable  ns  to  iinderftand  the  nature  of 
touch.  The  papillae  at  the  ends  of  the  lingers, 
fomewhat  larger  in  the  infide,  beautifully  difpofed 
in  fpiral  folds,  probably  fomewhat  erecled  by  the 
attention  of  the  mind,  as  appears  from  flriverings, 
from  the  nipples  of  women,  from  the  prolapfus  of  an 
intelline,  from  the  handling  of  tangible  objects,  and 
from  gentle  friction,  receive  the  impreflion  of  the 
object  on  their  nervous  fabric,  and  tranfmit  it  to  the 
trunks  of  the  nerves,  and  to  the  brain.  This  is  the 
fenfe  of  toueh.  It  enables  us  to  diftinguifh  chiefly 
the  roughnefs  of  objects  ; and  has  been  poflefled  to 
fo  exquilite  a degree  by  feme  perrons,  that  they  have 
been  known  to  diftinguilh  coloured  furfaces  by  the 
touch  alone.  We  perceive  heat,  when  external  bo- 
dies are  warmer  than  our  lingers  ; and  weight  like- 
wife,  when  they  gravitate  more  in  comparifon  with 
their  bulk  than  ufual.  Humidity  we  . judge  of  by 
the  prefence  of  adhering  water  ; foftnefs,  by  the 
yielding  of  the  object ; hardnefs,  by  the  }delding 
of  the  finger  ; figure,  by  the  hard  limits  circum- 
feribing  them  ; diitance,  by  an  inaccurate  calcula- 
tion derived  from  experience,  to  which  the  length 
of  the  arm  ferves  as  a meafure,  &c.  Touch  cor- 
rects the  errors  of  our  other  fenfes,  although  it 
fometimes  errs  itfelf,  and  though  other  fenfes,  in- 
dependent of  touch,  furnilli  animals  with  juft  per- 
ceptions. 

ccccxxxii.  The  mucous  body  of  Malpighius- 
moderates  the  action  of  the  object  touched,  and  pre- 
ferves  the  integrity  and  fofeneis  of  the  papiilce.  The 
cuticle  excludes  the  air  from  the  defanictiblc  fldn ; 
moderates  the  imprellions  of  bodies,  fo  that  they 
may  be  only  fufficient  to  affect  the  touch,  without 
cauling  pain  ; and,  therefore,  when  thickened  by 
life,  the  fenfe  of  feeling  is  loft  ; but,  if  it  be  too 
foft,  the  touch  becomes  painful.  The  hairs  defend 
the  cuticle  from  friction,  generate  and  preferve  the 


Chap.  XII. 


TOUCH. 


209 

heat,  conceal  fome  parts,  and  render  the  membra.nes 
of  others  irritable,  which  require  to  be  defended 
againft  the  entrance  of  infers  ; and  perhaps  they 
excrete  fomething  excrementitious,  and  afford  a paf- 
fage  to  the  exhaled  oil.  The  nails  are  fubfervient 
to  the  touch,  by  refilling  the  object  touched,  fo  as  to 
prevent  the  papillae  from  yielding,  and  being  bent 
back ; they  increafe  the  power  of  apprehenfion,  and 
affift  in  the  handling  of  minute  objects.  In  molt  ani- 
mals, they  ferve  as  weapons  of  offence  ; and  would 
be  of  the  fame  ufe  to  man,  if  they  were  not  cut. 

cc OCX XXIII.  Thefe  are  not  aU  the  ufes  of  the 
Ikin.  For  a moll  important  ofSce  of  that  covering 
is  to  exhale  from  the  body  a large  quantity  of  hu- 
mours, and  to  abforb  others  from  the  air.  Accord- 
ingly, the  whole  furface  of  the  fkin,  by  an  infinite 
number  of  fmall  arteries,  both  prolonged  into  the 
papillae,  and  feated  in  the  fkin  itfelf,  exhales  a va- 
pour which  exudes  through  correfponding  pores 
of  the  cuticle  ; but  when  the  polition  of  the  velfels 
is  changed,  it  is  eflufed  between  the  cuticle  and 
fkin.  Thefe  arteries  are  ealily  demonftrated  by  in- 
jecting water  or  ilinglafs  into  the  arteries  ; for  then, 
from  all'  parts  of  the  fkin,  an  infinite  number  of 
fmall  drops  exude,  which  being  effufed  under  the 
cuticle,  rendered  impervious  by  death,  raife  it  up 
in  blifters. 

ccccxxxiv.  During  life,  this  exhalation  is  de- 
monftrated in  many  ways.  A bright  mirror,  when 
held  near  the  warm  and  naked  fkin,  is  quickly  ob- 
fcured  by  a moift  vapour.  In  fubterraneous  cav- 
erns, where  the  air  is  denfer,  it  moft  evidently 
efcapes  into  the  air,  from  the  whole  furface  of  the 
body,  in  the  form  of  vifible  and  thick  clouds. 

ccccxxxv.  In  man,  and  in  fome,  though  not  in 
all  animals,  whenever  the  motion  of  the  blood  is 
increafed,  while  at  the  fame  time  the  fldn  is  hot 
and  relaxed,  from  the  fmall  cutaneous  pores,  in- 
ftead  of  an  invifible  vapour,  fweat  exudes  in  the 
P form 


^210 


TOUCH. 


Chap.  XB. 


form  of  minute,  but  vifible  drops,  which,  with  oth- 
ers of  the  fame  kind,  run  together  into  larger  drops. 
The  hotteft  parts  are  moil  fubjecl  to  fweat,  as  the 
head,  breaft,  and  folds  of  the  body.  The  experi- 
ment before  mentioned  (ccccxxxiii.)  together  with 
the  fimplicity  of  nature,  the  viuble  denfity  of  the 
cutaneous  and  pulmonary  exhalation  (ccccxxxiv.) 
perfuades  us,  that  fweat  is  difcha.rged  through  the 
fame  vefiels  which  are  the  organs  of  perfpiration, 
and  that  it  differs  only  in  its  quantity  and  celerity, 
and  by  the  admixture  of  the  liquor  of  the  febaceous 
glands  (ccccxxvii.)  and  the  fubcutaneous  oil, 
w'hich  being  diluted  by  the  more  plentifully  fecre- 
ted  arterial  fluid,  exude  of  an  oily  and  yellow  con- 
fiflence,  and  chieiiy  caufe  the  fmell  and  colour  of 
the  fweat.  Hence,  it  is  more  fetid  and  yellower  in 
the  armpits  and  groins,  where  thofe  glands  are 
moft  numerous.  Both  blood  and  fmall  fand  have 
efcaped  from  the  fkin  along  with  the  fweat. 

ccccxxxvi.  The  nature  of  perfpiration  mufl  be 
invefdgated  by  experiments,  and  by  its  analogy 
with  the  pulmonary  exhalation,  which,  in  like  man- 
ner, but  more  frequently  becomes  vifible  in  a cold 
air.  That  this  exhalation  is  chiefly  water,  has  been 
proved  by  experiments,  in  which  the  breath,  being 
received  into  large  veffels,  has  condenfed  into  wa- 
tery drops.  This  is  confirmed  by  the  tenuity  of 
the  cloud  on  the  mirror,  and  its  volatility,  and  by 
the  familiar  change  of  the  perfpired  matter,  when 
obflrucled,  into  a diurefis  or  diarrhoea,  and  from  the 
eafy  determination  of  wT.rm  liquors  to  affume  the 
form  of  perfpiration  by  heat,  or  of  urine  by  cold. 
This  w^ater  is  derived  from  our  drink,  which  fur- 
nifhes  a great  part  of  the  perfpiration,  and  from  in- 
halation. Frequently,  even  the  odours  of  our  ali- 
ments may  be  plainly  perceived  in  the  perfpiration  j 
there  is  alfo  an  admixture  of  the  electrical  mat- 
ter in  every  perfon,  and  in  fome  it  is  cHdently  lu- 
cid. 


CCCCXXXVII. 


Chap.  XIL 


TOUCH* 


2ii 


ccccxxxvii.  That  it  alfo  contains  fome  volatile 
particles  of  an  alkaline  nature,  is  evident,  both  from 
the  nature  of  our  blood,  and  from  the  confiderable 
evils  whiclf  fucceed  the  retention  of  the  perfpira- 
tion,  moft  confpicuouily  in  acute  difeafes,  when,  by 
being  repelled  inward,  it  renders  the  urine  pale, 
and  from  the  corruption  of  the  air  by  refpiration. 
This  volatile  alkadine  matter  arifes  from  the  parti- 
cles of  the  blood,  attenuated  by  perpetual  heat  and 
trituration,  and  changed  into  an  acrimonious  na- 
ture. Dogs  trace  thefe  odours,  and  could  not  know 
their  mafters  unlefs  fomething  of  a particular  nature 
were  perfpired  from  each  perfon. 

ccccxxxviii.  The  quantity  of  the  matter  perfpir- 
ed is  very  large,  whether  we  conlider  the  extent 
of  the  organ  fecreting  it,  the  quantity  of  vapour 
exhaled  by  the  lungs  alone,  or  the  experiments  of 
Sandtorius,  by  v/hich  it  would  feem,  that  of  eight 
pounds  of  food  and  drink,  five  pounds,  or,  according 
to  other  experiments  in  a colder  country,  from  thir- 
ty to  fifty-fix  ounces  areperfpired,  which  neither  add 
to  the  weight  of  the  body,  nor  efcape  by  any  vifible 
excretion,  except  the  fall va,  fweat,  and  mucus  of 
the  nofe.  But  the  cutaneous  exhalation  is  even 
much  larger  than  this  ; fince  it  not  only  throws  off 
fuch  a proportion  of  the  alimentary  matters,  but 
likewife  redifcharges  what  the  blood  acquires  by 
inhalation  (ccccxlii.)  In  this,  however,  the  dif- 
ferent fiates  of  the  air,  and  of  the  body,  have  great 
influence.  In  warm  countries,  in  the  fummer 
months,  and  in  young  active  perfons,  more  goes  off 
by  tranfpiration,  and  lefs  by  the  urine.  But  in 
cold  climates,  during  the  temperate  and  winter  fea- 
fons,  in  aged  Or  inactive  perfons,  more  goes  off  by 
the  urine  than  by  the  infenfible  perfpiration.  In  tem- 
perate countries,  making  a computation  throughout 
the  whole  year,  fomething  more  is  perfpired  than 
what  pafles  oft  by  urine  ; and,  by  collating  all  the 
experiments  m.ade  in  different  countries,  both  ex- 


0.12 


TOUCH. 


Chap.  XII. 


cretions  are  almoll  alike.  It  is  alfo  fomewhat  af- 
fected by  the  difference  of  time  after  eating  ; and 
the  law  which  feems  to  obtain,  is,  that  the  perfpi- 
ration  is  moft  copious  at  that  time  when  the  ali- 
mentary matters,  being  moftly  digefted,  and  receiv- 
ed into  the  blood,  are  fitted  for  exhalation.  It  is 
naturally  diminifhed  during  fleep,even  in  the  warm- 
er climates  ; but  it  is  increafed  by  the  heat  of  the 
bedclothes. 

ccccxxxix.  In  general,  a plentiful  and  equable 
perfpiration,  at  the  fame  time  that  the  body  is 
ftrong,  are  good  figns  of  health  ; for  exceffive  perf- 
piration, when  conjoined  with  debility,  is  obferved 
to  do  more  mifchief  than  its  entire  fuppreflion,  if 
what  has  been  written  on  this  fubjecl  is  fufficicnt- 
ly  to  be  depended  on.  It  is  a fign  of  health,  be- 
caufe  it  denotes  the  pervioufnefs  of  the  velfcls  dif- 
perfed  throughout  the  whole  body,  and  the  com- 
plete digellion  of  the  aliments,  of  which  a great 
part  is  refolved  into  halitus.  When  it  is  diminifli- 
ed,  it  indicates  conftridion  of  the  fkin,  weaknefs  of 
the  heart,  and  imperfe(5f  digellion.  When  excef- 
five, it  perhaps  waftes  the  nervous  fpirits.  This  dif- 
charge  is,  by  moderate  exercife,  increafed  to  fix 
times  that  of  a perfon  at  reft,  to  the  extent  of  a 
pound  in  an  hour,  or  even  in  half  an  hour.  It  is 
farther  increafed,  if  aided  by  ftrong  and  open  vef- 
fels,  by  warm,  watery,  and  cordial  drinks,  by  food  of 
eafy  digellion,  by  a denfe  and  temperate  atmofphere, 
and  by  cheerfulnefs.  It  is  diminiflied  or  fupprefl'ed 
by  the  contrary  caufes  ; as  a denfe  fkin,  a mioift,  or 
a cold  and  dry  atmofphere,  reft,  an  increafed  flow  of 
urine,  the  fupervention  of  a diarrhoea  ; and  hilly, 
nervous  aritation,  from  a difaereeable  affeclion  of 
the  m.ind.  Hocvever,  the  continuance  of  life  does 
not  depend  fo  intimately  on  this  difcharge,  which 
is  fo  eafily,  and  without  bad  confequences,  increal- 
cd  or  diminiflied  by  flight  caufes ; and  is  lb  incon- 
fiderable,  in  many  nations,anointing  their  fl?:ins  with 


Chap.  XII. 


TOUCH. 


213 


oil,  and  in  many  animals.  When  by  being  fup- 
preffed,  it  produces  fuch  bad  elFecls  in  fevers  of  a 
bad  kind,  it  hurts  chiefly  by  the  putrefcent  par- 
ticles, which  are  retained  by  the  perfpiration  being 
fupprelfed. 

ccccxL.  The  fweat  is  evidently  of  a faline  na- 
ture ; as  appears  both  from  its  tafte,  and  from  the 
cryftals  which  form  upon  the  clothes  of  glafs  blow- 
ers ; and  by  diftillation,  which  demonftrates  its  al- 
kaline nature.  Hence,  by  this  difcharge,  the  mi- 
afmata  of  the  moft  peftilential  dileafes  are  frequent- 
ly expelled.  But,  in  reality,  fweat  is  always  a pre- 
ternatural difcharge,  and  ought  never  to  exift  in  a 
healthy  perfon,  unlefs  by  violent  bodily  exerciie, 
he  have  induced  a temporary  difeafe.  It  alfo  is  fre- 
quently injurious  in  acute  difeafes  ; by  wafting  the 
water  of  the  blood,  fo  that  the  reft  becomes  thick- 
er, and  the  falts  more  acrimonious.  By  violent  ex- 
ercife,  or  the  heat  of  the  climate,  the  fweat  is  ren- 
dered extremely  fetid,  and  even  fanguineous ; be- 
ing elecftrical,  it  fometimes  is  lucid. 

ccccxLi.  The  ufes  of  perfpiration  are,  to  free  the 
blood  of  its  redundant  water,  of  its  alkaline  im- 
purities, rendered  more  acrid  by  repeated  circula- 
tions ; and  of  an  extremely  volatile  oil,  probably 
prepared  from  the  fame  blood.  The  fame  perfpi- 
ration likewife  qualifies  and  foftens  the  cuticle,  and 
preferves  the  neceflary  foftnefs  of  the  p^pills. 

ccccxLii.  But  the  fame  Ikin,  w'hich  has  veiTels 
exhaling  into  the  air,  is  likewife  replenifhed  with 
veflels,  which  abforb  thin  vapours  from  the  air, 
either  perpetually,  or  at  leaft  in  a moderate  degree 
of  cold  ; in  a moift  atmofphere  ; in  the  night  time, 
when  the  body  is  at  reft,  the  mind  deprefled,  and 
under  circumftances,  contrary  to  thofe  mentioned 
above,  (ccccxxxviii.)  which  increafe  perfpiration. 
Thefe  veins  are  demonftrated  by  anatomical  injec- 
tions, which,  if  thin  or  watery,  exude  through  them 
in  the  fame  manner  as  through  the  arteries  : 

moreover. 


214 


TOUCH. 


Chap.  XII. 


moreover,  by  the  manifeft  operations  of  medicines, 
diiTufed  in  the  air,  or  applied  to  the  fkin  ; of 
vapours,  mercury,  turpentine,  faffron  ; of  baths, 
mercurial  plafters,  tobacco,  coloquintida,  opium, 
cantharides,  arfenic  ; by  the  fatal  effecls  of  poifons, 
abforbed  by  the  Ikin  ; as  the  venereal  poifon  ; by 
the  living  of  animals,  without  drink,  in  hot  but  hu- 
mid illands ; by  the  perfpiration  and  urine  being 
fulliciently  copious  in  fuch  fituations,  without  much 
drink ; and  laftly,  by  extraordinary  morbid  cafes, 
in  which  the  quantity  of  urine  difeharged  has  far 
exceeded  the  drink  taken  in  ; in  which  it  is  proba- 
ble, that  the  inlialing  pores  were  more  open  ; for 
that  new  ones  were  generated,  is  not  credible.  It 
is  dilhcult  to  afeertain  its  quantity  ; that  it  is  very 
great  in  plants,  in*  the  night  time,  is  proved  by  cer- 
tain experiments. 

ccccxLiii.  Both  the  exhaling  and  inhaling  vef- 
fels,  may  be  contracted  and  relaxed  by  the  nervous 
power.  This  appears  from  the  effects  of  the  paffions 
of  the  mind ; which,  if  lively  and  exhilirating,  relax 
the  exhaling  veffels,  by  increafmg  the  impulfe  of 
the  influx  of  blood ; and  by  the  remiflion  of  the 
nerves ; hence  rednefs,  moilture,  and  turgefcence 
of  the  fldn.  Thofe  paflions  which  are  languid  and 
deprefling,  contract  the  exhaling  veffels  ; as  appears 
from  the  drynefs  of  the  fldn,  produced  by  them  ; 
from  the  goofe  fldn,  by  terror  ; and  from  diarrhoea, 
caufed  by  fear.  They  alfo  feem  to  dilate  the  inhal- 
insr  veffels,  whence  fear  facilitates  the  action  of  the 
fmaliuox  and  the  nlasrue. 

* A O 


CHAP, 


Chap.  XIII. 


TASTE. 


2^5 


CHAP.  XIII. 

TASTE. 

CcccxLiv.  I “'HE  organ  of  talle  differs  but  Illght- 
ly  from  that  of  touch.  It  appears, 
by  certain  experiments,  to  be  feated  in  the  tongue 
chiefly  ; for  neither  does  fugar,  applied  to  any  other 
part  of  the  mouth,  excite  the  leaf!  fenfe  of  tafte  in 
the  mind  5 nor  any  other  fapid  body,  unlefs  it  con- 
tain fomething  vehemently  penetrating  ; in  which 
cafe,  the  palate,  root  of  the  tongue,  uvula,  and  even 
the  cefophagus,  are  affecfled  by  the  fapid  acrimony. 
That  fenfation,  which  is  fometimes  excited  in  the 
ftomach,  cefophagus,  and  fauces,  by  the  regurgita- 
tion of  the  aliments,  feems  alfo  to  belong  to  the 
tongue,  to  which  the  fapid  vapours  are  applied. 

ccccxLv.  Onlythe upper  furface andlateral edges 
of  the  tongue  are  fitted  by  nature  to  exercife  the  fenfe 
of  tafle.  By  the  tongue  we  underhand  a mufcular 
body,  lodged  in  the  mouth,  obtufe,  very  broad  in 
man,  and  divided  in  the  middle  by  an  obfcure  fulcus. 
Its  poilerior  and  lower  parts  are  varioufly  connect- 
ed to  the  adjacent  bones  and  mufcles  ; its  anterior 
and  upper  parts  are  moveable.  In  that  portion 
which  conftitutes  the  organ  of  tafce,  the  fkin  con- 
tinuous with  that  of  the  face  and  mouth,  adheres  to 
the  mufcular  flelh,  but  is  pulpy  and  foft,  from  the 
perpetual  warmth  and  moiflure.  From  this  fkin 
arife  innumerable  nervous  papillae,  of  a more  con- 
fiderable  fize  here  than  in  other  parts.  Of  thefe 
there  are  fever al  kinds ; the  firft  kind  confifls  of 
nine  or  ten,  at  the  back  part  of  the  tongue,  difpof- 
ed  in  a line  on  each  fide  of  the  foramen  caecum. 
Thefe,  furrounded  by  a circular  groove,  for  the 
mofl  part  refemble  an  inverted  cone,  and  have  a deep 
finus  in  their  middle ; but  are  otherwife  hard,  and 
but  indifferently  adapted  for  tafdng,  although  you 

can 


2i6 


TASTE. 


Chap.  XIH. 


can  eafily  trace  nerves  into  them.  There  are  fome 
other  papillae  of  the  fame  kind  found  fcattered  be- 
fore thefe  upon  the  back  of  the  tongue. 

ccccxLvi.  Thefe  degenerate  into  the  fungiform 
clafs  of  papillae,  which  are  found  diftributed  over 
the  upper  furface  of  the  tongue,  lefs  and  flenderer 
than  the  former,  always  becoming  more  pointed  as 
they  proceed  forwards,  till  around  the  edges  of  the 
tongue  they  are  crowded  together,  and  difpofed  in 
diverging  lines.  The  third  fort  of  papillae  are  co- 
nical. Thefe  are  by  far  the  moft  numerous ; are 
difperfed  among  the  former,  and  are  fpread  copioufly 
over  the  tongue.  The  moft  anterior  of  them  in 
the  apex  of  the  tongue,  are  more  inclined  and  fluc- 
tuate ; they  are  moft  remarkably  numerous  in  the 
edges  of  the  tongue ; there  are  even  fome  behind 
the  foramen  cxcum.  They  are  highly  fenfible,  and 
conftitute  the  true  organ  of  tafte  ; other  papillae  arc 
intermixed,  partly  conical,  and  partly  filiform  ; and 
of  the  conical  ones  fome  are  larger,  and  others  fuc- 
ceflively  fmaller. 

ccccxLvii.  Thefe  papillae,  befides  numerous  vef- 
feis,  are  fapplied  with  nerves  which  may  be  traced 
into  the  larger  papillae,  and  with  which  the  tongue 
is  more  largely  fupplied  than  almoft  any  other 
part.  For,  befides  a nerve  of  the  eighth  pair, 
which,  with  one  of  its  principal  three  branches, 
enters  deeply  into  the  bafis  of  the  tongue,  covered 
by  the  cerato-glofliis,  near  the  os  hyoides ; there 
is  alfo  a confiderable  nerve  that  goes  to  the  mufcles 
of  the  tongue,  from  the  ninth  pair  ; which  having 
inofculated  with  the  firft  nerve  of  the  neck,  and 
with  the  large  cervical  ganglion,  and  having  fent  a 
branch  downwards,  often  uniting  with  the  eighth 
pair,  and  conftantly  with  the  fecond  and  third  of 
the  neck,  and  fupplying  the  mufcles  arifing  from 
the  fternum,  and  frequently  communicating  with 
the  phrenic  nerve,  proceeds  with  the  reft  of  its 
trunk  to  the  tongue.  This  communicates  in  the  ce- 

rato-glolTus, 


Chap.  XIII. 


TASTE. 


217 

rato-gloffus,  by  many  branches,  with  the  fifth  pair, 
and  is  chiefly  fpent  upon  the  genio-gloffus.  Lafl- 
ly,  the  third  branch  of  the  fifth  pair  having  fent 
upwards  or  received  the  cord  of  the  tympanum, 
and  given  other  branches  to  the  internal  pterygoid, 
and  biventer ; to  the  maxillary  gland,  forming 
with  thefe  a ganglion ; to  the  fublingual  gland, 
and  crofling  with  its  principal  trunk  the  cerato- 
glofius,  where  it  is  united  with  the  ninth  pair, 
comes  to  the  tongue,  in  company  with  the  deep 
feated  artery,  with  which  it  penetrates  to  the  tip 
of  the  tongue,  where  it  becomes  cutaneous.  To 
this  nerve,  therefore,  if  there  be  any  preference, 
the  fenfe  of  tafte  is  to  be  efpecially  afcribed,  which 
is  even  confirmed  by  morbid  examples.  Laftly, 
the  papillse  of  the  tongue  are  of  a hard  texture  ; a 
firm,  pulpy,  cellular  fubfiance  uniting  the  arteries, 
veins  and  nerves  into  malTes,  of  which  many  com- 
pofe  one  large  papilla. 

ccccxLviii.  The  arterial  and  venous  villi,  which 
run  between  the  papillae,  are  for  the  purpofes  of 
exhalation  and  inhalation,  and  have  nothing  to  do 
with  tafte,  farther  than  that  they  feparate  from  the 
blood,  a liquor  proper  for  diffolving  falts,  and  for 
keeping  moift  the  papillae,  which  they  pour  out  on 
the  back  of  the  tongue.  On  the  upper  and  back 
part  of  the  tongue,  are  feated  many  fimple  mucife- 
rous  glands,  opening  by  one  or  more  outlets,  and  of 
a round  lhape,  formed  by  an  hemifpherical  mem- 
brane, and  the  flefliy  part  of  the  tongue.  Some  of 
thefe  open  into  an  obfcure  blind  cavity,  of  an  un- 
certain figure,  -which  is  placed  in  the  middle  of  the 
largeft  papillae,  (ccccxlv.)  and  commonly  contains 
fome  of  them. 

ccccxLix.  The  papillae  of  the  human  tongue  are 
covered  only  by  a mucous,  femipellucid  m.embranc, 
which  adheres  clofely  to  them,  and  ferves  them  as 
a cuticle.  But,  in  animals,  a perforated  network 

receives 


21 8 TASTE.  Chap.  XIII. 

recehTS  the  papilis,  which  enter  into  hoUow  cor- 
nuted  Iheaths. 

ccccL.  Under  the  papiUa:  lies  the  mufcular  fub- 
ftance  of  the  tongue,  compofed  of  various  mufcles, 
but  in  man  hardly  extricable.  The  lower  part  is 
in  a great  meafure  made  up  of  the  genio-gloiius 
mufcle  extended  outwards  from  the  commiflure  of 
the  chin,  and  diftributcd  like  ra.ys  upon  the  tongue. 
The  upper  and  lateral  parts  are  compofed  of  the 
ftyio-glolfus,  whole  fibres  run  to  the  tip  of  the 
tongue.  Its  middle  part  between  thefe  is  compofed 
of  the  proper  lingual  mufcle,  which  arifing  from  it- 
felf  before  the  pharynx,  and  from  the  ftylo-gloffus, 
but  deeper,  proceeding  forwards,  is  terminated 
there,  and  in  the  genio-glofius  mufcle,  and  between 
that  and  the  ftylo-glofius,  conftitutes  a confiderabie 
part  of  the  tongue.  The  back  part  is  formed  by 
the  cerato-giofius,  of  which  the  fibres  afeend  up- 
v/ards  and  backv.^ards,  and  which  is  included  be- 
tween the  ftylo-gloffus  and  lingualis,  and  by  the 
chondro-gloftus,  an  entirely  different  mufcle,  which 
arifes  from  the  fmall  bones  of  the  os  hyoides,  and 
the  neareft  part  of  its  bafts,  from  whence  palling 
outwards,  covered  by  lateral  layers  of  the  genio- 
glofius,  and  joining  the  ftylo-gloffus,  it  difappears 
in  the  tongue.  By  the  action  of  thefe  mufcles,  the 
whole  tongue  is  moveable  in  all  directions,  and  is 
capable  of  varying  its  own  figure,  becoming  con- 
cave when  elevated  by  the  ftylo-giofii,  being  again 
flattened  by  the  cerato-glofTi,  being  rendered  nar- 
rower and  almoft  cylindrical,  by  the  tranfverfe  fibres 
of  the  tongue ; befides  which,  there  are  other  or- 
ders in  the  human  tong-ue  inextricable  and  inter- 

. r 

mixed  vcith  much  tenacious  rat. 

ccccLi.  The  arteries  of  the  tongue  are  numerous. 
The  largeft,  which  is  deep  feated  and  ferpentinc, 
comes  from  the  external  carotid,  a.nd  extends  along 
the  lower  part  to  the  tip  of  the  tongue  ; a fmallcr 
iuperfidal  artery,  incumbent  on  the  fublingual 

gland. 


Chap.  XIII. 


TASTE. 


219 

• 

gland,  and  inofculating  with  the  preceding,  arifes 
either  from  it,  or  from  the  labial.  Other  fmall  polle- 
rior  arteries  arife  either  from  branches  of  the  labial, 
or  from  the  tonfiilaris.  The  veins  of  the  tongue 
are  varioully  intricated,  and  difficult  to  defcribe ; 
one,  lying  deep,  accompanies  the  nerve  of  the  ninth 
pair  ; another,  fuperficial,  accompanies  the  mental 
arter}’-,  and,  inofculating  with  the  former,  forms 
the  ranular  vein ; but  all  of  them  tend  towards 
that  large  vein,  which  is  a different  branch  of  the 
internal  jugular,  from  the  cerebral  one.  They  va- 
rioufly  communicate  with  the  adjacent  tonlillary, 
thyroid,  pharyngeal,  and  cutaneous  plexufes ; and 
on  the  back  of  the  tongue,  before  the  epiglottis, 
thofe  of  the  right  and  left  lides  are  interwoven 
with  ’ each  other.  I find  lymphatic  veffels  rather 
in  the  neighbourhood  of  the  tongue,  than  in  the 
tongue  itfelf. 

ccccini.  The  papillce  of  the  tongue,  being  larger 
and  fofter  than  thofe  of  the  fldn,  and  perpetually 
moift,  perform  the  office  of  touch  more  exquifitely 
than  thofe  of  the  Ikin,  which  are  dry  and  fmall ; 
hence  the  tongue  fuffers  more  acute  pain : more- 
over, the  cutaneous  papillce  receive  no  other  fenfa- 
tions  from  falts  than  thofe  of  nioiffure  or  pain.  But 
the  papillae  of  the  tongue  being  ereded  and  fqme-' 
what  protuberant,  to  perform  the  office  of  tafte,  are 
affefted  in  fuch  a manner  by  falts  diffolved  in  water, 
or  faliva,  and  applied  to  their  fummits,  that  the 
mind  diftinguiffies  certain  claffes  of  tafte,  as  four, 
fweet,  rough,  bitter,  fait,  urinous,  fpirituous,  aro- 
matic, pungent  of  various  kinds,  infipid,  putrid, 
and  others  partly  purely  faline,  and  partly  changed, 
and  compounded  by  the  admixture  of  fubtile  ani- 
mal or  vegetable  oils.  All  very  acrid  falts  excite 
pain  inftead  of  tafte.  Does  the  diverfity  of  fla- 
vours arife  from  the  different  figures  of  the  falts  ? 
Does  this  appear  from  the  cubical  figure  of  fea- 
falt,  the  pri&i.aticai  figure  of  ifftre,  or  the  particu- 
lar 


720 


TASTE. 


Chap.  XIII. 


lar  configuration  of  vitriol,  fugar,  &c.  ? It  does  not 
fcem  probable,  for  even  infipid  cryftals  have  their 
particular  figures  ; and  in  falts,  very  different  in 
tafte  and  other  properties,  the  figures  are  too  much 
the  fame,  and  again  are  inconftant  in  the  fame  fait, 
as  for  example,  in  nitre,  which  may  by  art  be  ren- 
dered cubical.  The  caufe  of  tafte  feems  therefore 
to  refide  in  the  internal  ftruclure  of  the  elements, 
not  perceptible  by  our  fenfes. 

ccccLiii.  But  the  nature  of  the  covering  of  the 
papillae,  of  the  faliva,  of  the  fluids,  and  of  the  ali- 
ments lodged  in  the  ftomach,  have  great  influence 
on  the  perception  of  taftes  ; infomuch,  that  the 
fame  flavours  do  not  affect  all  ages  alike,  nor  all 
temperatures  ; nor  even  the  fame  perfon,  according 
as  he  may  be  in  health,  difeafed,  or  habituated  to 
it.  In  general,  whatever  contains  lefs  fait  than  the 
faliva  does,  feems  infipid. 

ccccLiv.  The  fpirituous  parts,  more  efpecially  of 
vegetables,  are  received  either  into  the  papillae  them- 
felves,  or  into  the  abforbing  villi  of  the  tongue  ; as 
appears  from  the  fpeedy  renovation  of  ftrength  by 
liciuors  of  this  kind,  even  when  they  are  not  taken 
into  the  ftomach. 

ccccnv.  Nature  defigned  the  diverfity  of  fla- 
vours, that  animals  might  know  thofe  things  moft 
proper  for  their  food  : for  in  general,  there  is  no 
aliment  unhealthy,  that  is  of  an  agreeable  tafte  ; 
nor  is  any  thing  ill  tailed  that  is  fit  for  the  food 
of  man.  We  here  take  no  notice  of  excefs,  by 
which  the  moft  healthy  food  may  become  prejudi- 
cial, or  of  minerals,  which  are  not  furniflied  by  na- 
ture, but  prepared  by  art.  Thus  nature  has  invit- 
ed man  to  take  the  food  necelfary  for  his  fubfdt- 
ence,  both  by  the  pain  called  hunger,  and  by  the 
pleafure  arifing  from  tafte.  But  animals,  which 
do  not  learn  from  example  and  the  inftruction  of 
others,  diftinguifla  flavours  more  accurately,  and, 
admoniflied  by  that  teft,  abftain  cautioufly  from 

unhealthy 


Chap.  XIV. 


SMELL. 


unhealthy  food ; and,  therefore  herbiverous  ani- 
mals efpecially,  to  which  a very  great  diverfity  of 
aliments  mixed  with  noxious  plants  are  offerol, 
are  furniilied  with  fuch  long  papillae,  and  fo  ele- 
gant a ftruclure  of  the  tongue,  for  which  man  has 
lefs  occafion. 


CHAP.  XIV. 

SMELL. 

ccccLvi.  i the  fame  ufe  of  difcerning  preju- 
I dicial  food,  the  fenfe  of  fmelling  is 
fubfervient ; by  which  we  both  perceive  their  nox- 
ious nature,  before  they  be  tailed,  which  might  be 
dangerous ; and  efpecially  avoid  putridity  in  our 
vi duals,  which  to  us  is  exceedingly  hurtful ; and 
difcover  what  is  grateful  and  wholefome ; although 
by  habit,  this  advantage  of  fmell  is  more  confpicu- 
oiis  in  animals  than  in  man.  But  men  who  have 
been  left  to  themfelves,  and  whofe  fenfe  of  fmell  has 
not  been  corrupted  by  variety,  have  been  obferved 
moll  certainly  to  retain  that  fagacious  faculty  in 
dillinguilhing  food  in  an  eminent  degree.  Final- 
ly, the  powers  of  medicinal  plants  are  hardly  to  be 
eftimated  better  than  by  the  limple  tellimonies  of 
talle  and  fmell.  Hence,  in  all  animals  the  organ 
of  fmell  is  placed  near  the  mouth ; and  hence  the 
fmell  is  ftronger,  and  the  organs  larger,  in  thofe 
animals  which  have  to  feek  their  prey  at  a conlid- 
erable  dillance,  or  to  rejed  deleterious  plants  from 
among  their  food. 

ccccLvii.  The  fenfe  of  fmelling  is  performed  by 
means  of  a foft,  pulpy,  vafcular,  papillous,  porous 
membrane,  which  lines  the  whole  internal  cavity 
of  the  nollrils,  and  is  thicker  upon  the  feptum  and 
principal  cavity  of  the  nofe,  but  thinner  in  the 
hnufes.  It  is  plentifully  fupplied  with  very  foft 

nerves. 


222 


SMELL. 


Chap.  XIV. 


nerves,  the  middle  ones  of  which  defcend  from  the 
firft  pair,  (ccclvii.)  through  the  holes  of  the  os  cri- 
brofum  to  the  leptum  narium  ; but  in  fuch  a man- 
ner that  it  is  very  difficult  to  trace  them  to  their 
extremities  and  into  the  feptum.  Other  lateral 
nerves  come  from  the  fecond  branch  of  the  fifth 
pair  and  its  branches,  from  that  which  crofTes  the 
pterygoid  canal,  and  from  another  which  defcends 
through  the  canals  of  the  palate  ; and  in  the  max- 
illary linus  from  the  infra-orbital  branch,  from  the 
dental  branch,  and  from  the  anterior  nerve  of  the 
palate.  Moreover,  the  anterior  part  of  the  feptum 
has  a twig  from  the  ophthalmic  of  the  firft  branch 
of  the  fifth  pair. 

ccccLviii.  The  noftrils  are  fupplicd  wath  very 
numerous  arteries  ; from  the  three  nafal  branches 
of  the  internal  maxillary,  above  from  both  the  eth- 
moidal branches,  and  the  frontal  and  nafal  branch- 
es, with  lateral  arteries  from  the  fmaller  ophthalmic 
branch  of  the  internal  carotid,  and  from  branches 
of  the  palatine  artery,  and  in  the  finufes  from  the 
ihfra-orbitrd,  and  from  the  fuperior  dental  one. 
Thefe  arteries  have  the  property  of  exuding  blood 
eafiiy,  and  in  great  quantity,  Avithout  any  lefion  of 
confequence.  The  correfpondent  veins  form  a ve- 
ry large  plexus  upon  the  external  pterygoid  muf- 
cle  ; then  communicate  with  the  finufes  of  the  du- 
ra mater  ; and,  laftly,  meet  in  the  external  branch 
of  the  internal  iugular.  The  arteries  fupply  nour- 
ifiiment,  warmth,  and  mucus. 

ccccLix.  The  head,  efpeciaily  in  man,  being  of 
a fpherical  figure,  confines  the  organ  of  fmell  with- 
in a fmall  fpace.  That  it  may  be  extended  inter- 
nally, the  noftrils  have  been  made  complicated  and 
cavernous  in  a furprifihg  manner.  In  the  firft 
place,  the  noftrils  are  thaTpiultiform  cavity  which 
begins  at  the  anterior  openings  of  the  nofe,  and, 
extending  tranfverfely  backwards  over  the  roof  of 
the  palate  under  the  ethmoid  bone,  terminatCvS  at 

the 


Chap.  XIV. 


SMELL. 


the  cavity  of  the  fauces.  This  cavity  is  divided  by 
a feptum,  often  unequally,  which  is  bony  in  the 
upper  part,  and  defcends  from  the  plate  of  the  eth- 
moid ; below,  it  is  formed  by  the  vomer,  and  in  its 
forepart  it  conlifts  of  a triangular  cartilage,  whofe 
furface  is  large  and  very  fenfible. 

ccccLX.  Moreover,  the  lateral  furfaces  of  the 
nares  are  increafed  by  the  fpiral  convolutions  of 
the  offa  turbinata  ; the  uppermoft  of  which  are  the 
fmall  faperior  and  pofterior  convolutions  of  the  eth- 
moid bone.  The  muddle  ones  belong  to  the  fame 
bone,  are  of  a long  conchoid  form,  convex  inwards, 
externally  concave,  pointed  at  both  ends,  covered  all 
over  with  pits,  and  internally  filed  with  fpongy 
cells  fufpended  tranfverfely,  and  fupported  by  par- 
ticular eminences  of  tlie  palate  and  maxillary  bones. 
The  low^eil  turbinata  are  fxmilar  to  the  middle 
ones  ; like  them  refemble  in  figure  a limpet  flieli, 
but  longer  ; are  for  the  moft  part  divided  from  the 
former,  but  fiometimes  conjoined  by  a bony  plate 
which  is  m.ofi;  frequently  of  a membranous  nature. 
This  appendix,  being  extended  upwards  in  a fquare 
form,  completes  the  maxillary  finus. 

ccccLxi.  The  cavity  of  the  noftrils  is  ftill  fur- 
ther enlarged,  by  means  of  the  various  finufes, 
which  are  recefles  or  a kind  of  appendages  to  the 
noftrils.  The  uppermoft  of  thefe  are  the  frontal 
finufes,  wLich  are  inconftant  and  irregular,  feated 
in  the  fuperciliary  ridge,  and  fituated  betwixt  the 
anterior  and  pofterior  plates  of  the  frontal  bone. 
T"hey  are  not  found  in  the  foetus,  and  feem  to  arife 
from  the  action  of  the  corrugator  and  other  mufcles, 
which  draw  the  anterior  plate  outw*ards,  and  in- 
creafe  the  diploe  into  cells,  in  the  fame  manner  as 
in  the  maftoid  procefs.  Thefe  open  in  the  upper 
part  of  the  noftrils  into  the  anterior  cell  of  the  os 
papyraceum.  There  are  inftances  of  their  being 
totally  w^anting,  and  growing  after  birth. 


CCCCLXIL. 


124 


SMELL. 


Chap.  XIV. 


ccccLxn.  The  fecond  in  order  are  the  ethmoi- 
dal finufes  ; of  which  four  or  more  on  each  fide 
are  found  in  the  outer  part  of  the  os  cribofum,like 
the  cells  of  an  honey  comb  ; above,  they  are  com- 
pleted by  the  cellular  diploe  of  the  os  frontis,  be- 
fore by  the  os  unguis,  and  behind  by  the  palate  and 
fphenoidal  bone  ; they  open  into  the  upper  part  of 
the  noftrils  in  a tranfverfe  line,  by  many  fmall  tubes, 
even  placed  one  above  another.  With  thefe  are 
continuous  the  cells  in  the  bottom  of  the  orbit,  and 
thofe  excavated  in  the  os  planum  and  maxillare 
are  outwardly  continued  from  them.  In  the  third 
place,  the  large  cavity  of  the  multiform  bone  on 
each  fide  is  alfo  contiguous,  and  in  fome  meafure 
belongs  to  the  ethmoid  and  palate  bones.  By  the 
drying  up  of  the  cartilage,  which  is  here  of  large 
extent  in  the  foetus,  it  gradually  is  formed  in  the 
folid  bone,  under  the  fella  turcica,  is  capacious, 
either  fingle  or  divided,  and  opens  forwards  by  its 
aperture  into  the  upper  paflage  of  the  noftrils. 

ccccLxiii.  The  laft,  loweft,  and  largeft  of  the 
finufes,  which  in  the  foetus  exifts  in  fome  degree, 
but  in  the  adult,  by  the  attenuation  of  the  bony 
laminae,  becomes  very  large,  is  chiefly  excavated  in 
the  upper  maxillary  bone.  Its  opening  into  the 
noftrils  is  bounded  by  the  os  unguis,  bone  of  the 
palate,  proper  lamella  of  the  loweft  os  turbinatum, 
and  by  membranes,  fo  that  it  enters  by  a round 
aperture  between  the  middle  and  loweft  fpongy 
bones.  But  it  likewife  fends  forth  an  hollow  ap- 
pendix, ftretching  forwards  under  the  orbits,  which 
is  formed  by  the  os  planum,  unguis,  and  papyra- 
ceum,  communicating  likewife  with  the  ethmoidal 
cells,  and  opening  behind  the  oftium  lachr)"male. 

ccccLxiv.  The  nerves  of  the  nofe,  being  almoft 
naked,  require  a defence  from  the  air,  which  is 
continually  infpired  and  expired  through  the  nof- 
trils, for  the  purpofes  of  refpiration.  Nature  has 

therefore 


Chap.  XIV. 


SMELL. 


225 

therefore  fupplied  the  noftrils,  in  place  of  a thicker 
cuticle,  with  a vifcid,  bland,  inlipid  mucus,  fluid 
at  its  firft  feparation,  but  by  the  air  condenling  in- 
to thick  dry  crufts,  and  more  confiftent  here  than 
in  other  parts  of  the  body.  By  this  mucus  the 
nerves  are  defended  from  drying  and  from  pain. 
It  is  poured  out  from  the  very  numerous  fmall  ar- 
teries of  the  noftrils  ; and  is  depofited  partly  into 
numerous  cylindrical  du6ts,  and  partly  into  round 
vilible  cryptse,  fcattered  throughout  the  noftrils. 
The  fame  mucus  exudes  over  the  furface  of  the 
whole  olfadlory  membrane,  and  every  where  anoints 
it.  In  the  feptum,  a long  finus,  common  to  many 
muciferous  pores,  runs  forwards  a confiderable  way. 
The  mucus  accumulated  in  the  night  time,  in  too 
great  quantity,  is  expelled  during  the  day  by  com- 
prelEng  the  noftrils,  and  forcing  the  breath  through 
them  ; or  by  its  drynefs  and  acrimony,  it  irritates 
the  very  fenfible  nerves,  and  is  then  expelled  by  the 
fneezing  excited.  But  the  finufes  which  abound 
Vvdth  mucus,  evacuate  it  according  to  the  different 
poftures  of  the  body ; by  fome  of  them  always  be- 
ing at  liberty  to  difcharge  it,  whether  the  head  be 
erect  or  inclined  forwards,  or  to  the  fide  ; yet  fo, 
that  generally  the  maxiUary  and  fphenoidal  finufes 
are  more  difficultly  emptied  than  the  reft.  More- 
over, the  tears  defcend  through  a proper  duct  into 
the  noftrils,  and  moiften  them,  and  dilute  the  mucus. 

ccccLxv.  The  extremities  of  the  noftrils  are  cov- 
ered by  the  nofe,  which  is  lined  inwardly  with  a 
membrane  of  the  fame  nature,  and  is  com.pofed  of 
two  bones,  and  ufually  fix  cartilages,  two  of  which 
are  continuous  vfith  the  middle  feptum  (cccclix.) 
The  nofe  may  be  moved  by  its  mufcles,  fo  as  to 
be  raifed  and  dilated  by  a mufcle  common  to  it  and 
the  upper  ftp,  and  to  be  contracted  by  its  proper 
deprellor  and  compreffor,  and  depreffor  of  the  lep- 
tum.  Thus  the  organ  of  fmell  is  prominent;  and 
cxpofed  to  the  aCtion  of  odours,  and  may  be  dilated 
Q for 


smUll. 


Chap.  XIV. 


226 

for  taking  in  a larger  quantity  of  air,  and  again  be 
coiitracled,  when  the  fuperabundance  is  expelled. 

ccccLxvi.  The  air,  therefore,  filled  with  the 
very  fubtile,  invifible,  pungent,  oily,  faline,  and  vol- 
atile effluvia,  which  exhale  from  almoft  every 
known  body,  being  received  into  the  noftrils,  by 
the  aclion  of  refpiration,  (cclxv.)  and  by  a pecu- 
liar effort  for  drawing  the  air  into  them,  carries 
thefe  particles  to  the  nerves,  widely  naked,  and 
conftantly  foft.  By  thefe  there  is  excited  in  thefe 
nerves  a kind  of  fenfation  which  we  call  fmeil,  by 
which  we  diftinguifh  the  feveral  kinds  of  oils  and 
falts,  in  a manner  fomewhat  indiffinef,  diflicultly 
reducible  to  claffes,  difficultly  recalled  to  the  mem- 
ory, neverthelcfs  fufficiently  for  our  purpofes. 
This  fenfe  informs  us  of  unwliolefome  putridity,  of 
exceffive  acrimony,  and  of  the  bland  and  ufeful  na- 
ture of  fubftances.  And  as  fait,  united  with  oil,  is 
an  object  of  tafte,  and  as  oils,  combined  with  falts, 
conftitute  odours,  the  affinity  of  the  two  fenfes, 
which  was  neceffary  to  derive  utility  from  either, 
is  apparent.  But  volatile  particles  chiefly  are 
diffinguiflied  by  fmeil,  and  fixed  ones  by  the  tafte  ; 
perhaps  becaufe  the  thick  mucous  cuticle,  fpread 
over  the  tongue,  intercepts  the  aclion  of  the  more 
fubtile  falts,  which  eafily  affecl:  the  fofter  and  lefs 
covered  nerves  of  the  noftrils.  Wc  are  ignorant 
of  the  reafons  why  fome  fmeils  pleafe,  and  others 
difpleafe  ; perhaps  cuftom  may  have  fome  influ- 
ence in  this  refpecl. 

ccccLxvii.  The  action  of  fmeils  is  ftrong,but  of 
fhort  continuance  ; becaufe  particles  in  a very  mi- 
nute ftate  are  applied  to  naked  nerves,  in  the  im- 
mediate vicinity  of  the  brain.  Hence  the  delete- 
rious and  refrefiiing  actions  of  odours,  by  which 
people  are  refufeitated  from  faintings,  and  even  from 
drovming.  Hence  the  violent  fneezing,  excited  by 
acrid  particles,  the  evacuation  of  the  bowels,  by  the 
fmeli  of  purgatives,  and  the  power  of  antipathies. 

Hcncc 


HEARING. 


Chap.  XV. 


227 


Hence  the  pernicious  effects  of  exceffive  fneezing, 
more  efpecially  blindnefs,  from  the  great  fympathy 
of  the  nerves.  Amongft  the  various  parts  of  the 
noftrils,  the  feptum,  and  the  offa  turbinata,  and 
their  anterior  portions,  efpecially  form  the  organ 
of  fmell : fince  thefe  parts  are  multiplied  in  quick 
fcented  animals,  forming  beautiful  fpires  in  quadru- 
peds ; and  in  fifli,  being  diftributed  in  parallel  la- 
minae elegantly  toothed. 

CHAP.  XV. 


HEARINGi 

ccccLxviii.  A S the  fenfe  of  fmelling  diftinguifh- 
es  the  fmall  bodies  which  float  in 
the  air,  hearing  perceives  the  tremors  of  the  elafdc 
air  itfelf.  Therefore,  the  fenfltive  organ  of  the 
ear  is  compofed  in  a different  manner  from  that  of 
any  of  the  other  fenfes  ; as  it  is  in  a great  part 
made  up,  either  of  elaftic  cartilages,  or  hard  bones, 
that  it  may  communicate  with  accuracy  the  tre- 
mors received. 

ccccLxix.  The  external  organ  of  this  fenfe  is 
the  ear,  or  that  cartilage  which  is  connected  before 
and-  behind  to  the  bones  of  the  temple,  by  ftrong 
cellular  fubftance  and  proper  ligaments,  with  fome 
degree  of  mobility,  which  is  diminifhed  by  habit. 
This  cartilage  is  of  a compound  figure ; in  its  general 
fhape,  oval,  but  divided  by  projecting  convolutions 
and  intermediate  grooves,  to  which  other  hollows 
and  ridges  correfpond  in  the  oppofite  furface.  The 
outer  eminence,  called  helix,  arifes  above  the  loofe 
lobe,  and  furrounding  the  ear,  terminates  in  a pro- 
jedting  line  dividing  the  concha;  Below  it,  lies  the 
anthelix,  a bifurcated  eminence,  forming  a ridge 
Contained  within  the  former,  and  terminating  in  a 
ftiort  tongue  called  the  antitragus.  The  remaining 
0^  2 part 


Chap.  XV. 


HEARING, 

part  of  tlie  ear  hollow  before,  and  convex  behind, 
growing  gradually  deeper,  having  a projecting  line 
running  through  its  middle,  is  called  the  concha, 
and  is  joined  with  the  meatus  auditorious,  which  is 
protected  by  a neai'ly  round  moveable  appendix, 
called  the  tragus. 

ccccLxx.  All  this  part  of  the  ear  is  only  cover- 
ed by  a thin  fkin,  and  lean  cellular  fubftance  ; and 
is  replenillied  with  many  febaceous  glands,  fupply- 
ing  an  ointment.  It  is  moved  by  certain  mufcles, 
■ivhich  generally  become  ufelefs,  from  habit  and 
the  cuftom  of  binding  them,  which,  however,  it  is 
probable  were  appointed  by  nature  to  perform 
certain  ofSces;  The  uppermoft  of  thefe  mufcles 
arifes  thin  from  the  frontal  and  from  the  aponeu- 
rofis  of  the  cranium  ; whence  it  is  broadly  fpread 
over  the  aponeurohs  of  the  temporal  mufcle,  and 
is  inferted  into  the  anthelix,  or  neighbouring  helix, 
at  the  anonymous  cavity.  The  pofterior  mufcles, 
which  are  two  or  three,  or  more  or  lefs,  are  more 
robuft  than  the  former,  almoft  trahfverfe,  and  arif- 
ing  from  the  aponeurohs  of  the  cervical  mufcles,  and 
from  the  membraites  adhering  to  the  maftoid  pro- 
cefs,  are  inferted  into  the  convex  part  of  the  conch, 
and  without  doubt  dilate  it.  The  anterior  mufcle 
is  the  leaft  j this  alfo  is  fpread  upon  the  aponeurolis 
of  the  temporal  mufcle,  and  is  inferted  almoft  train-  ; 
verfely  into  the  origin  of  the  helix  and  into  tlie  j 
neighbouring  concha.  But  fmaller,  fliort  mufcles,  | 
hardly  diftinguifhable,  though  fomewhat  red , proba- 
bly make  fome  change  in  the  ear  itfelf.  The  tranf-  < 
verfe  mufcle  of  the  ear,  joining  the  concha  with  I 
the  concave  back  part  of  the  anthelix,  opens  the  ear.  ^ 
The  antitragicus,  defeending  from  the  root  of  the 
anthelix  to  the  upper  part  of  the  antitragus,  widens 
the  entrance  of  the  conch.  The  tragicus,  which  lies 
upon  tlie  tragus,  and  is  almoft  fquarc,  dilates  the  i 
aperture ; the  mufculus  inciftirie  majoris,  lies  be-  I 
tween  the  middle  and  third  cartilages  of  the  nudi-  i 

torr 


HEARING. 


22§ 


Chap.  XV. 

tory  paffage,  brings  them  nearer  together,  and  ren, 
ders  the  meatus  itfelf  more  elaftic.  The  remaining 
mufcles,  the  longer  or  larger,  and  the  leffer  of  the 
helix,  have  hardly  any  great  ufe  ; perhaps  they 
have  fome  influence  when  we  wifh  to  hear  weak 
founds  more  accurately,  and  tighten  the  organ  of 
hearinir,  and  render  the  meatus  auditorious  firmer 
by  drawing  together  the  cartilages, 
ccccLXXi.  With  the  concha  is  connected  the  mea- 
tus auditorious,  of  a round  compreffed  figure,  in.; 
dined  inwards,  leffening  as  it  proceeds,  about  the 
middle  bent  forwards,  and  for  a confiderable  part 
bony.  But,  in  its  anterior  and  outer  part,  it  is 
partly  formed  of  three  imperfec):  rings,  the  firft 
arifing  from  the  tragus,  the  fecond  from  the 
concha,  and  the  third  from  the  other  two,  con- 
neded  with  each  other  by  intermediate  mufcle, 
memibrane,  and  cartilage,  and  finally  adhering  to 
the  bone  itfelf.  The  upper  and  back  parts  of  the 
meatus  are  formed  by  mere  membrane.  This 
is  the  ftate  of  it  in  adidts ; for,  in  the  foetus  and, 
new  born  infant,  the  meatus  is  wholly  cartilaginous, 
and  its  olTeous  part  is  gradually  formed. 

ccccLxxii.  Into  this  auditory  pafiage  are  con, 
tinued  the  cuticle  and  true  fkin,  which  are  gradu- 
ally extenuated  and  exactly  ftretched  over  the 
bone,  and  are  therefore  very  fenfible  of  any  irrita- 
tion, pleafure  or  pain  ; and  by  the  irritable  hairs 
with  which  it  is  furnifhed,  intimation  is  given  of 
the  accumulation  of  any  fordes,  and  of  the  entrance 
of  infeds.  In  the  cellular  fubftance,  which  is 
fomewhat  indurated  and  reticulated,  efpecially  in 
the  membranous  portion,  (cccclxxi.)  there  are  nu- 
merous yellow  round  follicles,  which,  by  fliort  duds, 
depofite  into  the  cavity  of  the  auditory  paffage  a 
liquid,  at  firft  oily,  but  afterwards  becoming  gra- 
dually thick,  bitter,  and  inflammable,  which  lines 
the  fenfible  fkin  and  membrane  of  the  tymna- 
tipm,  and  defends  them  from  the  air,  and  drives 

away 


HEARING. 


Cha:?.  XV. 


230 

away  or  keeps  back  infects ; but,  when  accumula- 
ted in  flothful  or  uncleanly  perfons,  it  caufes  deaf- 
ncfs. 

ccccLXxiii.  Into  the  ear  the  fonorous  waves  of 
the  air  flow,  which,  from  the  principles  of  me- 
chanics, it  collects.  The  elaftic  air  receives  fono- 
rous vibrations  ; and  particularly  tranfmits  them, 
although  fome  other  bodies  alfo  propagate  fonorous 
vibrations,  either  alone,  or  at  leaf!  in  the  greateft 
degree,  if  indeed  water  deprived  of  air  be  capable 
of  vibrating.  Hence,  found  is  increafed  in  air  that 
is  condenfed,  and  is  loft  in  vacuo.  The  air  receives 
thefe  tremors,  either  from  fome  body  ftriking  a- 
gainft  it,  or  from  fome  body  againft  which  it  rufh* 
es,  or  laftly  from  the  mutual  coUifion  of  bodies. 
But  a body  which  produces  found,  muft  vibrate 
and  ofcillate  in  all,  even  in  the  leaft  of  its  particles, 
fo  as  to  form  alternate  arches  riling  up  from  the  for- 
mer ftraight  furface,  and  returning  beyond  the  fame. 
This  fpecies  of  curved  line  is  called  the  excedens  of 
the  founding  body.  The  tremor  impels  the  neareft 
wave  of  air,  and  thus  the  anterior  portion  of  air 
being  comprefled,  as  foon  as  its  elafticity  over- 
comes the  impelled  trem.or,  rebounds  and  repels  the 
air  towards  the  founding  body,  where  the  air  is  now 
more  rarefied  and  thin,  and  cempreffes  it.  The  fame 
portion  of  air,  ftruck  by  the  founding  body,  in  like 
manner  impels  the  portion  of  air  contiguous  to  it, 
which  alfo  reacting  in  due  time,  repels  the  tremu- 
lous air  backwards  towards  the  body,  and  for- 
wards to  produce  a new  wave.  Thefe  ofcillations 
muft  thus  fucceed  each  other  quickly,  to  render 
them  audible,  and  iiiuft  not  be  fewer  than  30  in 
a fecend. 

ccccLXxiv.  Acute  founds  are,  in  general,  emit- 
ted from  bodies  that  are  hard,  brittle,  and  very 
tenfe : grave  founds  are  connected  with  the  contra- 
ry  properties.  Thofe  founds  .in  general  are  called 

acute 


Chap.  XV. 


HEARING. 


231 

acute,  which  are  produced  by  more  frequent  vibra- 
tions in  a given  time ; and  thofe  obtufe,  which  are 
produced  by  lefs  frequent  vibrations.  There  is  no 
limit  between  acute  and  grave  founds,  but  what  is 
arbitrary.  Cords,  or  other  bodies,  that  yield  the 
fame  number  of  vibrations  in  a given  time,  are  faid 
to  be  in  unifon.  Octaves  are  produced  when  the 
one  makes  double  the  number  of  ofcillations  that 
the  other  does  ; other  proportions  have  different 
names  affigned  to  them.  The  fhorter  cords  pro- 
duce the  fliarpeft  tones,  and  the  reverfe,  in  the  in- 
verfe  proportion  of  their  lengths ; they  are  alfo 
more  acute  as  they  are  tenfer  in  the  fubduplieate 
proportion  of  their  tenlion,  or  the  weights  by  which 
they  are  ftretched.  Experiments  to  this  purpofe 
are  very  eafily  made  vdth  a monocord,  or  a feries 
of  cords  ftretched  by  weights. 

ccccLxxv.  Sound,  however  produced,  whether 
acute  or  grave,  ftrong  or  weak,  is  carried  through 
the  air  with  a velocity  equal  to  about  1038  Paris 
feet  in  a fecond,  and  that  with  an  uniform  velocity, 
without  being  diminiflied  by  great  diftances.  But 
a contrary  wind,  although  much  flower,  retards  in 
fom.e  degree  the  progrefs  of  found,  and  takes  away 
about  of  its  velocity.  So  likewife  denfity  and 
drynefs  of  the  air  increafe  found ; rarefaction  and 
moifture  diminifti  it.  The  heat  of  fummer  augments 
its  velocity  ; in  Guinea,  it  has  been  tranfmitted  at 
the  rate  of  1098  Pariftan  feet  in  a fecond. 

ccccLxxvi.  Every  found  meets  with  particles  in- 
all  adjacent  bodies,  even  in  \vater  and  mercury,  in 
which  it  excites  fimilar  vibrations,  not  only  in  fuch 
as  are  in  unifon,  which  yield  a more  evident  found, 
but  alfo  in  other  particles,  which  vibrate  in  a dif- 
ferent ratio.  Hence  every  found  which  vx  hear, 
is  a mixture  of  the  primitive  tone,  produced  by  the 
vibrating  body,  and  of  the  fecondary  tones  gene- 
rated by  the  elaftic  tremors  of  the  furrounding  bo- 
dies, The  ftrength  of  found  is  increafed,  if  the  fe- 

eondarjy 


HEARESTG. 


Ghap.  XV. 


condary  founds  fucceed  the  primary  one  fo  quickly, 
that  they  cannot  be  difcriminated  by  tlie  ear  ; but 
if  fo  llowly  as  to  be  diftinguifhable  by  the  ear,  they 
produce  an  echo ; but  this  requires  an  interval  of 
fix  thirds  of  time,  or  the  diftance  of  55  feet  betwixt 
the  body  returning  the  found  and  the  ear. 

ccccLxxvii.  Sound  is  reflected  from  hard  bodie*^ 
in  angles  equal  to  thofe  of  its  incidence.  But  found 
emitted  into  the  open  air,  being  diffufed  through 
an  immenfe  fphere,  grows  weaker  ; when  fent 
through  a cylinder,  it  retains  its  ftrength,  and  when 
coiiecfed  into  the  focus  of  an  ellipfe,  as  in  th.e  fpeak- 
ing  trumpet,  it  is  increafed,  as  it  ifl'ues  from  the  fo- 
cus of  the  parabola  in  parallel,  not  in  diverging 
lines. 

ccccLXxviii.  Therefore  the  fonorous  undulations, 
propagated  through  the  air,  ftrike  upon  our  ear, 
placed  in  an  elevated  fituation,  and  naturally  in- 
clined forwards  and  outwards.  As  that  is  elaftic, 
they  arc  reverberated ; and  by  alternate  refleclions, 
they  are  collected  into  the  concha,  and  into  the 
meatus  auditorious,  where  they  become  as  much 
flronger,  as  the  furface  of  the  car  is  larger  than  the 
caliber  of  the  meatus.  Through  that  paflage,  in 
fomc  mcafure  cylindrical,  they  proceed  inwards  un- 
diminifhed,  and  increafed  by  new  rcfonances,  ex- 
cited by  the  percufiion  of  the  elaftic  cartilages 
and  hard  bones,  and  blended  with  the  primitive 
found. 

ccccLxxix.  The  internal  end  of  the  meatus  au- 
ditorious is  terminated  by  the  membrana  tympani ; 
in  adults  it  is  obliquely  applied,  of  a roundifh  figure 
but  having  an  appendix  above,  projects  inwards 
like  a flrield,  fo  that  the  lower  half,  concave  to- 
wards the  meatus,  projects  as  the  bofs  into  the 
cavity  of  the  tympanum,  and  the  upper  half  is  con- 
cave towards  the  tympanum,  and  convex  towards 
the  meatus.  This  m^embrane  is  compofed  of  leve- 
ral  plates ; the  firft  is  v.-hiteand  mucous,  net  a per- 


•HEARING. 


Chap.  XV. 


n ^ H 


feet  membrane,  and  in  the  foetus  only ; then  the  epi- 
dermis ; and  then  the  true  Ikin,  continuous  with 
the  membrane  of  the  meatus,  and  vafcular  ; the 
third  is  dry,  rattling,  ihining,  pellucid,  and  with- 
put  blood-veffels.  It  is  formed  from  the  periofteuni 
of  the  meatus,  and  of  the  tympanum.  Some  tender 
cellular  texture  intervenes  between  thefe.  This 
membrane  is  not  naturally  perforated  with  any 
opening,  fo  far  as  I have  been  able  to  difeover,  and 
the  tranfmiffion  of  fmoke  is  fabulous.  It  is  con- 
ftantly  ftretched  in  the  groove  of  the  ring  in  which 
it  is  contained,  which  is  proper  to  the  foetus,  but 
after  the  birth  coalefces  with  the  reft  of  the  os  pe- 
trofum,  fo  that  there  is  no  part  of  the  human  body 
more  tenfe  or  more  tremulous  than  this.  Upon 
the  furface  of  this  membrane,  and  more  efpecially 
upon  its  conical  cavity  pointing  inv/ards,  the  fono- 
rous  waves  ftrike,  after  their  laft  refledlion  in  the 
auditory  paflage,  and  on  account  of  its  elafticity, 
force  it  to  vibrate. 

ccccLxxx.  This  membrane  is  ftretched  over  a 
cavity  of  the  os  petrofum,  called  the  tympanum  ; 
which  is  in  general  of  an  irregularly  roundifli  fig- 
ure. It  is  divided  in  its  middle  by  a promontory, 
and  in  the  adult  it  is  increafed' backwards  by  the 
cells  of  the  maftoid  bone,  which  in  the  foetus  are 
wanting.  The  tympanum  is  cellular  alfo  before, 
above  and  behind.  ' It  is  lined  with  a vafcular 
membrane,  receiving  fmail  branches  from  the  in- 
ternal carotid,  from  the  branch  of  the  artery  of  the 
dura  mater,  which  paffes  through  the  fiffure  in  the 
aqueduff,  and  from  the  external  arteries  of  the 
tympanum,  and  from  the  llylo-maftoidea.  It  is 
commonly  full  of  mucus,  poured  into  it  from  the 
Euftachian  tube,  and  is  divided  into  a kind  of  cells 
by  different  membranes,  which  are  productions  of 
tile  periofteum  to  the  ollicula  auditus. 

cccci-xxxr.  Within  this  cavity,  the  little  bones 
of  hearing  are  fituated,  three  of  them  being  lar- 
ger. 


HEARING. 


Chap,  TV. 


234 

ger,  and  the  fourth  lefs.  The  round  head  of  the 
malleus,  its  upper  part,  is  fituted  in  the  roof  of  the 
tympanum,  from  whence  its  long  handle  defeends 
between  the  laminae  of  the  membrane  of  the  tym- 
panum, as  far  as  its  middle,  accurately,  tied  to  it, 
with  a broad  extremity  a little  incurvated  outwards. 
It  is  alfo  connected  with  the  long  crus  of  the  incus 
by  a peculiar  ligament ; another  membrane,  near  its 
long  procefs,  fattens  the  malleus.  A Ihort  and  co- 
nical procefs  above  its  handle,  prefles  the  membrane 
of  the  tympanum  outwards.  From  the  fame  place, 
a procefs,  very  long,  comprefied,  and  fomewhat 
broad,  but  of  a variable  figure,  extends  forwards  in- 
to a fulcus  of  the  tube.  The  head  of  the  malleus  is 
articulated  with  the  incus  by  two  protuberant  lines, 
and  an  intervening  fulcus,  all  of  them  oblique. 

ccccLxxxii.  Three  mufcles  are  commonly  deferi- 
bed,  as  belonging  to  the  malleus  ; the  firtt  and  lar- 
gett,  the  tenfer  tympani,  is  internal,  and  is  lodged 
in  a particular  canal  of  the  tube,  to  which  it  runs 
parallel,  arifing  from  a procefs  of  the  multiform 
bone  between  the  pattage  of  the  cerebral  carotid  and 
the  hole  of  the  artery  of  the  dura  mater  ; it  is  infec- 
ted by  its  tendon  rcttecled  downwards  and  out- 
wards, around  a pully,  into  the  beginning  of  the  han- 
dle. The  fecond  mufcle  arifes  from  a fulcus,  con- 
neetted  with  the  fame  tube,  but  external  to  it,  ftiorter 
than  the  former  ; and  carried  backwards  almoft  in 
the  fame  manner,  but  without  being  reflected,  it  ad- 
heres by  a confiderable  extent  to  the  longer  pro- 
cefs ; its  luufcularity  is  doubted,  not  being  re- 
markably different  from  red  pulpy  membrane. 
The  third,  which  is  faid  to  arife  from  the  auditory 
paflage,  to  enter  the.  tytnpanum,  through  a notch 
in  the  imperfect  ring,  to  be  infected  juft  by'  the 
flrorter  procefs  into  the  malleus,  and  to  relax  the 
membrane,  has  never  been  feen  with  fuflicient  cer- 
tainty', either  by  myfelf,  or  by  the  mott  eminent 
anaiomitts.  The  tenfor,  by  means  of  the  mallcu>, 

■ada^t:^ 


HEARING. 


Chap.  XV. 


235 


adapts  the  membrane  of  the  tympanum  for  the 
hearing  of  weak  founds  ; the  fecond  mufcle,  if  it 
exift,  moderates  thofe  that  are  too  powerful,  by 
drawing  the  malleus  from  the  incus,  and  in  that 
way,  interrupting  the  propagation  of  the  fono- 
rous  tremors.  If  the  membrane  of  the  tympanum 
be  broken,  or  the  fmall  bones  difplaced,  the  hear- 
ing firft  becomes  dull,  and  afterwards  perfect  deaf- 
nefs  enfues  ; that  part  of  hearing  only  being  left, 
which  is  propagated  through  the  bones  of  the 
Ikull. 

ccccLxxxiii.  The  malleus  imparts  the  tremors 
which  it  receives  from  the  membrane  of  the  tympa- 
num, to  the  incus,  which  is  a fhort  thick  little  bone, 
articulated  with  it  behind  by  a broad  furface,  with 
two  fulci  and  a middle  eminence.  The  Ihorter  leg  of 
this  bone,  whofe  little  body  is  bifurcated,  is  notch- 
ed, fufpended  by  a ligament,  and  is  held  firm  in 
a peculiar  fulcus  of  bone.  The  other  leg  defcends 
farther,  parallel  to  the  malleus  ; and,  by  its  ex- 
tremity bent  inwards,  is  adapted  to  the  fourth 
bone,  which  it  receives,  being  convex  on  that  fide, 
and  flat  on  the  other,  and  refts  upon  the  frapes,'  to 
which  it  communicates  its  vibrations. 

ccccJLXxxiv.  The  ftapes,  aptly  fo  called  from  its 
figure,  lies  in  an  inclined  pofition,  with  a hollow 
head  which  receives  the  incus,  with  curved  crura,  ef- 
pecially  the  pofterior  one,  and  with  an  oval  bafis,  but 
flatter  below,  with  which  it  fills  a hole  correfponding 
to  it,  commonly  called  the  feneftra  ovalis.  The  cru- 
ra, which  are  fulcated  inwardly,  are  joined  by  a 
denfe  membrane  affixed  to  the  flightly  hollow  bafis. 
The  ftapes  is  governed  by  its  own  mufcle,  which  be- 
ing included  in  a bony  papilla,  fends  out  a fmall  ten- 
don, which  proceeds  forwards,  and  is  inferted  under 
the  incus  into  the  head  of  the  ftapes.  It  feems  to  draw 
the  ftapes  fo  that  its  pofterior  part  may  enter  deep- 
er into  the  feneftra  ovalis,  and  its  anterior  part  ad- 
yance  outwards.  Thus  the  nervous  pulp  of  the 

veftibulum 


HEARING. 


Chap.  XV. 


236 

veftibuliim  is  compreffed,  both  by  the  bafis  of  the 
ftapes,  and  by  the  air  of  the  tympaniim.  The  whole 
feat  of  the  ftapes  is  feparated  from  the  reft  of  the 
tympanum  by  a peculiar  membrane. 

ccccLxxxv.  A fmaU  roundifti  oval  bone,  flightly 
excavated  on  both  ftdes,  is  connected  by  one  fide 
with  the  longer  leg  of  the  incus,  and  by  the  other 
with  the  head  of  the  ftapes. 

ccccLXxxvi.  Various  canals  pafs  out  from  the 
cavity  of  the  tympanum.  Above  the  two  larger 
bones,  behind  the  pofterior  leg  of  the  incus,  is  a 
fmall  cell,  a kind  of  appendix  to  the  tympanum,  of 
the  figure  of  a gnomon.  Behind  it,  the  cells  in  the 
os  petrofum  begin  above  the  mamillary  procefs. 
Below  thefe,  that  procefs  is  excavated  in  the  adult 
with  various  cells. 

ccccLxxxvii.  Bcfides,  a peculiar  canal,  proceed- 
ing forwards  from  the  anterior  extremity  of  the 
tympanum,  emerges  from  the  bones  between  the 
fphenoid  and  temporal  bones,  and  correfponds  ufith 
an  elliptical  diverging  cone,  partly  cartilaginous, 
of  uncertain  ftructure,  and  partly  membranous, 
which  opens  behind  the  noftrils  into  the  ca^'ity  of 
the  fauces,  by  a very  large  elliptical  aperture,  turn- 
ed inwards  and  forwards  ; it  is  lined  with  a porous 
membrane,  full  of  cryptae,  continuous,  and  fimilar  to 
the  membrane  of  the  nares.  This  forms  the  Eufta- 
chian  tube,  whicli  by  the  aclic^  of  the  circumjacent 
mufcles,  may  be  comprefied,  and  probably  a little 
relaxed  and  opened  again,  by  the  circumflex  mufcle 
of  the  moveable  palate.  By  this  canal,  the  air,  dur- 
ing infpiration,  enters  int©  the  tympanum  to  l>e 
changed,  and  the  mucus  is  poured  around  the  little 
bones  to  defend  them  : nor  is  it  improbable,  that 
the  air  iiTues  out  of  this  tube,  when  the  tympanum 
is  prefled  inwards  by  powerful  founds ; likewife, 
founds  received  into  tlie  mouth,  are  conveyed  by  it 
to  the  organ  of  hearing.  In  infpiration,  the  air 
prefles  the  membrane  of  the  tympanum  outwards  •, 

hcnQ<^ 


Chap.  XV. 


HEARING. 


^3^ 

hence  the  humming  and  dulnefs  of  hearing  in 
yawning  ; for  then  the  air  entering  in  greater  quan- 
tity into  the  tube  and  tympanum,  refifts  the  tre- 
mors of  the  external  air. 

ccccLXxxviii.  Two  other  paflages  lead  from  the 
tympanum  to  the  labyrinth,  or  innermoft  part  of 
the  ear.  The  feneftra  ovalis,  (cccclxxxiv.)  not 
covered  by  any  membrane,  leads  into  the  veftibu^ 
ium  ; which  is  a round  cavity,  excavated  in  the 
very  hard  petrous  bone,  and  lies  near  the  inner 
part  of  the  tympanum^  In  that  cavity  there  is  a 
fuperior  elliptical  recefs,  an  inferior  circular  one, 
and  a third  refembling  a groove.  There  is  a ner- 
vous pulp  in  the  veftibulum,  feparated  from  its 
bony  fides  by  vapour  furrounding  it.  Into  this  the 
five  mouths  of  the  three  femicircular  canals,  the 
foramen  ovale,  and  the  paflages  of  the  nerves  and 
arteries  open. 

ccccLxxxix.  In  the  foetus,  the  canals  are  formed  of 
a diftind:  hard  fhell,  which  is  furrounded  with  fpon- 
gy  bone  ^ in  adults,  they  are  excavated  in  the  excef- 
fively  hard  petrous  bone,  fomething  larger  than  fe- 
micircles,  and  have  ample  openings.  The  larger  pof- 
terior  and  lower  of  thefe  is  perpendicular  ; alfo 
the  middle  and  upper  one  is  placed  perpendicular- 
ly j but  the  outermofl;  and  leafl:  is  horizontal.  The 
inner  mouth  of  the  uppermoft  unites  with  the  up- 
per opening  of  the  pofterior. 

ccccxc.  But  the  cochlea  is  ftill  more  wonderful. 
It  is  feated  in  an  inclined  pofition  in  the  anterior 
portion  of  the  os  petrofum.  Into  its  one  cavity  the 
veftibulum  opens,  and  into  the  other  the  feneftra 
rotunda  of  the  tympanum,  which  being  covered  by 
the  promontory,  lies  hid  in  the  bottom  of  the  tym- 
panum. The  cochlea  itfelf  is  compofed  of  a nu- 
cleus of  bone,  of  a conical  figure,  with  its  apex  in- 
clined inwards  ; divided  into  tubes,  which  are  call- 
ed fcalae,  by  a middle  fulcus,  which  is  perforated,, 
both  in  its  bafis,  and  through  its  whole  length,  by 

innumerable 


HEARING. 


Chap.  XV. 


23S 

inmimerable  fmall  foramina,  and  terminates  in  the 
middle  of  the  fecond  fpiral.  About  this  nucleus 
are  wrapt  two  turns  and  a half  of  a canal ; %vhich, 
in  the  foetus,  is  diftincl,  and  has  its  own  flaell ; but, 
in  the  adult,  is  united  with  the  adjacent  bone,  and 
diminiflies  conically  from  the  two  openings  men- 
tioned above,  towards  the  apex  of  the  nucleus. 
This  canal  is  bilocular,  and  divided  by  a partition 
called  lamina  fpiralis,  of  which  the  greateft  part  is 
bony,  and  arifes  from  the  nucleus,  projecting  from 
it  at  right  angles  into  the  hollow  canal,  is  ftriated, 
and  included  on  both  fides  in  the  internal  periof- 
teum  as  in  a capfule.  The  remaining  and  exterior 
portion  is  membranous,  which  completes  the  divi- 
lion  of  the  canal : thus  there  are  formed  two  dif- 
tinct  femicanals,  called  fcalse.  The  interior  and  pofte- 
rior  of  thefe  begins  from  the  fcneltra  rotunda,  where 
it  is  firut  by  a membrane,  and  is  called  the  fcala 
tympani ; the  other  anterior  one  arifes  from  the 
vellibulum,  from  which  it  has  its  name.  From  the 
apex  of  the  nucleus  a third  cavity  originates,  fhap- 
cd  like  a funnel.  Into  this  the  fpiral  lamina  ter- 
minates by  a membranaceous  extremity,  but  fo  that 
the  funnel  comiRumicates  with  each  fcala,  by  one 
fmall  hole  on  each  fide,  and  by  many  ^\’ith  the  cav- 
itv  of  the  modiolus,  which  is  filled  with  nerve. 

ccccxci.  The  blood-velTels  of  the  outer  ear  come 
from  the  tanporal,  and  proper  auricular  branches  ; 
thofe  of  the  membrane  of  the  tympanum  from  the 
temporal,  from  the  ftylo-maftoideal,  or  from  both  j 
thole  of  the  meatus  auditorius  come  from  the  fame  ; 
thofe  of  the  tympanum  were  defcribed  (cccclxxx.) 
and  the  velTels  belonging  to  the  veftibulum,  cochlea, 
and  femicircular  canals,  are  from  the  vcrtebralis  and 
ftylo-maftoidealis  and  meningea.  The  induftry  of 
late  anatomifts  has  traced  abfcrbent  veflels  of  a par- 
ticular kind,  from  the  veftibulum  into  the  tranf- 
verfe  finusj  from,  the  cochlea  into  the  cavity  of  the 
Ikull. 


CCCCXCI  I. 


HEARING. 


Chap.  XV. 


23$ 


ccccxcii.  It  now  remains  that  we  defcribe  the 
nerves  fubfervient  to  the  fenfe  of  hearing,  of  which 
the  principal  is  that  called  the  feventh,  (ccclvii.) 
This  nerve  enters  into  the  internal  auditory  fmus 
of  the  os  petrofum,  in  the  blind  end  of  which  it 
divides.  The  fmaller  part  of  the  nerve  enters 
through  the  upper  opening  in  the  linus,  into  a ca^ 
nal,  which  is  at  firft  tranfverfe,  and  afterwards  re- 
fledfed  behind  the  tympanum.  While  it  defcends 
there,  it  gives  off  a branch  through  a peculiar  ca- 
nal to  the  tympanum,  which  afcends  betwixt  the 
malleus  and  incus,  goes  out  of  the  tympanum, 
through  a fiffure  behind  the  articulation  of  the 
lower  jaw,  and  inferts  itfclf  into  the  nerve  of  the 
tongue,  (ccccLvii.)  the  reafon  of  which  fecret  com- 
munication is  obfcure,  but  ferves  to  explain  the 
fympathy  between  the  teeth  and  lliarp  founds,  and 
burning  of  the  ear,  &c.  The  reft  of  the  nerve, 
efcaping  by  the  fide  of  the  ftyloid  procefs,  is  diftri- 
buted  on  the  external  ear,  the  parotid  gland,  a large 
part  of  the  face,  and  upper  part  of  the  neck,  both 
cutaneous  and  mufcular  ; and  in  the  face,  forms 
numerous  inofculations,  both  betwixt  its  own 
branches,  and  wdth  thofe  of  the  firft,  fecond,  and 
third  of  the  fifth  pair  ; with  the  eighth  pair,  and 
with  the  third  cervical  pair.  To  the  organs  of 
hearing,  it  fends  either  no  branches,  or  very  fmall 
ones.  The  anterior  part  of  the  outer  ear  receives 
other  nerves  from  the  third  branch  of  the  fifth  pair, 
and  the  pofterior  part,  from  the  fecond  and  third 
cervicals. 

ccccXciil.  But  the  foft  portion,  which  is  larger, 
but  more  obfcure,  arifes  by  very  minute  filaments, 
from  the  fourth  ventricle  of  the  brain  itfelf, 
(ccclvii.)  and  enters  through  exceeding  fmaU  holes 
of  the  inner  auditory  finus,  in  part  with  from  three 
to  five  branches,  into  the  veftibulum,  and  in  part 
into  the  fulcus  of  the  cochlea.  Thefe  branches  in 
the  veftibulum  form  three  pulpy  maffes,  which  com.^ 

bine 


240 


HEARING. 


Chap.  XV. 


birxC  to  form  the  membrane  fufpended  in  the  vefti- 
bulum,  and  which  is  continued  through  the  whole 
of  the  femicircular  canals.  The  other  part,  which 
enters  the  fulcus  of  the  cochlea,  has  an  obfcure  ter- 
mination. 

ccccixciv.  With  refpccl  to  the  nerve  which  is 
diftributed  upon  the  veftibulum  and  femicircular 
canals,  there  is  no  doubt  that  it  is  affected  by  tlie 
tremors  of  the  external  air,  propagated  to  the  Rapes  ; 
which  reach  the  pulp  of  the  naked  nerve,  through 
the  feneftra  ovalis.  That  part  of  the  neiwe,  which 
enters  the  cochlea,  is  altogether  lefs  underftood. 
ft  is  probable,  that  fmall  branches  from  thence  pafs 
through  the  little  foramina,  (ccccxc.)  to  the  peri- 
ofteum  of  the  cochlea,  and  to  the  membranous  part 
of  the  lamina  fpiralis.  Do  tranfverfe  nervous  fila- 
ments, fucceflively  lliorter,  pafs  out  from  the  nu- 
cleus of  the  cochlea,  along  the  lamina  fpiralis? 
Is  it  the  organ  of  hearing  ? Thefe  are  queftions, 
which  we  are  yet  hardly  able  to  refolve  from  anat- 
omy ; though  the  example  of  birds  and  fiflies, 
which  hear  exquifltely  without  a cochlea,  feems  tp 
negative  them.  However  this  may  be,  it  is  pro- 
bable, that  the  fpiral  plate,  full  of  nerves,  is  ex- 
cited to  vibration  by  the  ofcillations  of  the  mem- 
brane of  the  tympanum,  which  agitate  the  air  in 
the  cavity  of  the  tympanum,  fo  that  it  impinges  on 
the  membrane  of  the  round  feneftra,  which  again 
agitates  the  air  contained  in  the  cochlea. 

ccccxcv.  It  is  an  elegant  conjechire,  that  fince 
the  lamina*  fpiralis  forms  a true  triangle,  of  which 
the  apex  is  a very  acute  angle,  it  may  be  fuppol- 
cd  to  contain  an  infinite  number  of  cords,  fuc- 
cefTively  flicrter,  which  correfpond  harmonically, 
(ccccjLXxiv.)  with  the  various  acute  and  grave 
tones,  fo  that  tliey  vibrate  in  unifon  with  the  greateft 
number  of  founds  ; the  longeft  cords  in  the  bafisof 
tlie  cochlea,  with  the  graveft  founds  •,  and  the  flrort- 


Chap.  XV. 


HEARING. 


241 


efl  cords  neareft  the  apex,  with  the  fliarpeh  founds. 
Are  founds  perceived  in  the  middle  femicircular 
canals,  fince  thefe  alone  are  found  in  all  clalfes  of 
animals  ? Or  are  they  perceived  in  thefe  canals,  in 
the  cochlea,  and  in  the  membrane  fufpended  in  the 
veftibulum  ? This  feems  probable. 

ccccxcvi.  It  appears  that  the  audable  elaftic  un- 
dulations of  the  air,  pafs  through  the  outer  ear 
and  auditory  paffage,  to  the  membrane  of  the  tym- 
panum ; for  when  it  is  injured,  and  not  repaired, 
the  hearing  is  totally  deftroyed.  It  feems  to  be 
ftretched,  for  hearing  w'eak  founds,  by  the  mufcles 
of  the  malleus;  From  this  membrane,  the  found 
is  propagated  through  the  fmall  bones  to  the  vefti- 
bulum ; for  thefe  bones  being  deftroyed,  the  hear- 
ing is  again  aboliftied.  The  bony  fides  of  the  vef- 
tibulum vibrate,  and  agitate  the  aqueous  fluid  fur- 
rounding the  nervous  pulp*  By  it,  the  nervous  pulp 
fufpended  in  the  veftibulum,  feems  to  be  affeded, 
and  that  tremor  to  be  continued  through  the  con- 
tinuous pulp  of  the  cochlea  and  femicircular  canals. 
Nothing  farther  is  known  : but,  by  undoubted  ex- 
periments, elaftic  fonorous  tremors  affect  the  audi- 
tory nerve,  through  the  intervention  of  the  Eufta- 
chian  tube,  of  the  teeth,  and  of  ail  the  bones  of  the 
IkulL 

ccccxcvm  The  diftinftion  of  founds,  without 
doubt,  proceeds  from  the  velocity  of  the  tremors 
excited  in  the  auditory  nerve,  according  as  they 
fuceed  each  other  more  fwiftly  or  flowly  ; it  is  not 
neceffary  the  mind  Ihould  number  them  ; it  is  fuf- 
ficient  that  the  different  numbers  excite  different 
changes  in  the  mind.  Does  the  gratefulnefs  of 
founds  arife  from  the  number  of  confonances  ? Does 
the  mind,  inconfdcufly,  number  the  degrees  of  con- 
fonance,  and  derive  pieafure  from  their  facility  and 
frquency  ? Thefe  are  denied  by  the  moft  expert 
mufidans,  vho  prove,  that  much  pieafure  proceeds 
R from 


242 


SIGHT. 


Chap.  XVI. 


from  founds  having  very  little  concordance,  and  re- 
lated in  very  difficult  proportions.  Why  are  too 
acute  founds  intolerable  ? They  feem  to  ftrctch 
our  nerves  in  the  lamina  fpiralis  to  fach  a degree, 
that  they  are  even  ruptured,  as  glaffes  are  broken  by 
acute  founds,  and  the  Ihrill  whifilino;  of  canarv 
birds  almoll  deftroys  the  power  of  hearing. 


CHAP.  XVI. 


SIGHT. 


CCCCXCVIII. 


’TEARING  is  the  perception  of  the 
J.  vibrations  of  the  air  ; fight  per- 
ceives thofe  of  light : the  organ  of  hearing  is  bony, 
that  it  may  admit  of  refonance  ; the  organ  of  vi- 
fion  chiefly  confifls  of  humours,  which  refract : the 
complex  nature  of  this  organ  was  rendered  necef- 
fary  for  the  defence  of  parts,  fo  very  tender,  and 
by  the  diverfity  of  the  humours,  to  be  contained 
each  in  its  proper  integuments. 

ccccxcix.  The  moft  external  defence  of  the  eye 
is  afforded  by  the  eyebrow,  which  is  a protuber- 
ance of  the  fkin,  fuftained  by  mufcles,  at  the  bot- 
tom of  the  forehead,  full  of  thick  imbricated  hairs, 
and  along  with  the  frontal  mufcle,  capable  of  being 
pulled  down  by  the  action  of  the  corrugator,  and 
orbicular  mufcles,  fo  as  to  afford  a ffiade  to  the  eye 
in  too  ftrong  a light.  After  the  eyebrow  has  com- 
pleted its  functions,  it  is  again  raifed  by  the  frontal 
mufcle,  which  is  inferted  into  it,  thin  and  flefhy, 
immediately  under  the  continuous  fkin,  faflened  to 
the  cellular  membrane  of  the  fkull,  which  is  finn- 
ing, not  very  unlike  an  aponeurofis,  and  is  drawn 
back\vards  by  the  rectangular  occipital  mufcle.  The 
deprefiion  of  the  eyebrow  denotes  care,  its  eleva- 
tion, tranquillity  and  ferenity  of  mind.  It  alfo  turns 

afidc 


Chap.  XVI.  SIGHT.  243 

alide  the  courfe  of  the  fweat,  and  keeps  off  infects 
from  the  eye. 

D.  The  eyelids  furnifti  a nearer  protection  to 
the  eye.  Thefe  are  folds  of  the  Ikin,  proceeding 
from  that  of  the  face,  extenuated,  lengthened  out 
into  an  edge,  as  if  divided,  reflected  upon  itfelf, 
and  retracing  the  courfe  of  the  former  lamina, 
from  which  it  is  feparated  by  fome  cellular  fub- 
ftance  ; then  having  become  membranous,  vafcular, 
and  therefore  red,  and  thin,  it  is  carried  over  the 
ball  of  the  eye,  under  the  denomination  of  con- 
junctiva tunica,  and  covers  the  anterior  portion  of 
the  fclerotica,  and  finally  the  cornea.  The  epider- 
mis accompanies  it  in  its  whole  courfe,  even  where 
it  adheres  to  the  cornea.  The  upper  eyelid  is  larg- 
er, and  more  moveable  : the  lower  is  fmaller  ; and 
rather  paflive,  than  moved  by  any  power  of  its 
own.  The  nerves,  which  give  fenfibility  to  the 
eyelids,  are  numerous,  from  the  firft  and  fecond 
branches  of  the  fifth  pair,  and  from  the  portio  dura 
of  the  feventh ; they  abound  with  arteries  from 
the  ophthalmics,  temporals,  branches  of  the  inter- 
nal maxillaries,  infra  orbitals,  and  facials. 

Di.  That  the  eyelids  may  fhut  together  more 
exactly,  each  of  them  has  a cartilaginous  arch,  call- 
ed tarfus,  upon  that  margin  which  touches  tlie 
other.  It  is  flender,  of  a lunar  figure,  extenuated 
outwards,  and  ftretches  the  eyelid,  preventing  the 
formation  of  folds  while  it  is  elevated  or  depreffed. 
The  elevation  of  the  upper  eyelid  is  performed  by 
a peculiar  mufcle,  arifing  from  the  involucrum  of 
the  Optic  nerve  gradually  fpreading,  and  continued 
by  its  expanfion  to  the  tarfus.  This  is  confiderably 
affifted  in  its  aClion  by  the  frontalis,  which  is  vari- 
oufly  connected  with  the  orbicularis,  and  draws  it 
upwards.  The  upper  eyelid  is  depreffed  by  the 
orbicularis,  as  it  is  called  ; a broad  mufcle,  both 
widely  expanded  around  the  orbit,  and  contained 
in  the  eyelids,  carried  as  far  as  both  angles  of  the 
R 2 eye. 


SIGHT. 


Chap.  XVI. 


^44 

eye,  and  having,  as  fixed  points,  the  ligament  ad- 
hering to  the  procefs  of  the  maxillary  bone,  and 
fome  fibres  inferred  into  the  frontal  and  upper  jaw 
bone.  The  fame  mufcle  elevates  the  lower  eyelid, 
and  covers  the  eye  in  fach  a manner  that  no  dull 
or  light  can  enter  it  during  fleep.  The  lower  eye- 
lid is  depreffed  by  two  bundles  of  fibres,  inferred 
into  the  upper  lip. 

Dll.  Finally,  that  the  tumid  m.argins  of  the  eye- 
lids may  not  flint  too  clofely,  they  are  provided 
with  eyelaflies,  or  fringes  of  hair  fpreading  out- 
wards, proceeding  in  many  rows  from  the  edges 
of  the  eyelids,  which,  by  decuffating  each  other, 
increafe  the  fhade  and  obfeurity.  Thefe  are  of  ufe 
in  more  difUncf  vifion,  by  excluding  the  extrane- 
ous rays,  when  we  require  a diftincf  reprefentation 
of  any  objeci:. 

Din.  The  eyelids  are  prevented  fi’om  hurting 
each  other  by  the  febaceous  glands  of  Meibomius, 
confifling  of  thirty  or  more  follicles  in  each  eyelid, 
which  arc  fimple,  bifid  or  trifid  ; placed  in  general 
according  to  the  length  of  the  lid,  and  compofed  of 
peculiar  blind  roundifli  cavities,  which  unite  into 
one  larger  ferpentine  duel,  of  which  the  orifice  is 
in  the  margin  of  tlie  evelid  itfelf.  Thefe  difcharjje 
a fort  unctuous  liniment,  which  mixes  and  waflies 
off  with  tlie  tears. 

Div.  But  the  perpetual  attrition  caufed  by  the 
eyelids  afeending  and  defeending  againft  the  globe 
of  the  eye  is  prevented,  the  delicacy  of  the  cornea 
is  preferved,  and  any  infects  or  other  irritating  fub- 
Itances  which  may  have  got  into  the  eye,  are  wafli- 
ed  away  by  the  tears  ; a faline,  pellucid,  and  evap- 
orable  liquor,  which  never  ceafes  to  be  poured  over 
the  anterior  furface  of  the  eye,  but  never  runs 
over  the  cheeks,  unlcfs  accumulated  from  fome 
caufe.  This  liquor  is  exhaled  partly  from  the  ar- 
teries of  the  conjunctiva,  as  we  fee  from  an  imita- 
tion  of  nature  by  injecting  water  j and  in  part  it  is 

believed 


Chap.  XYl. 


SIGHT. 


245 


believed  to  proceed  from  a gland  feated  in  a hollow 
recefs  of  the  os  frontis,  fomewhat  hard,  and  of  the 
conglomerate  kind  : divided  into  many  lobes,  inter- 
mixed with  fat,  and  fupplied  with  many  blood-vef- 
fels  from  the  ophthalmics  and  internal  maxillaries  ; 
and  pervaded  by  many  nerves  arifing  from  a pecu- 
liar branch  of  the  firft  trunk  of  the  fifth  pair. 

Dv.  From  this  lachrymal  gland,  fix  or  more  vi- 
fible  ducts  defcend,  which  open  on  the  inner  fide  of 
the  conjunctiva  of  the  eyelid.  In  man  thefe  dufts 
have  been  lately  difcovered  by  credible  authors. 
The  fecretion  of  the  tears  is  increafed  by  the  re- 
peated contractions  of  the  orbicular  mufcle,  either 
from  irritation,  or  fome  depreffing  paflion,  by 
which  means  the  tears  are  conveyed  over  the  whole 
eye,  and  the  furface  of  the  conjunctiva  is  waflied. 

Dvi.  After  the  tears  have  performed  their  oflice, 
fome  part  of  them  being  evaporated  by  the  air,  the 
reft,  that  they  may  not  prove  injurious  by  their  ac- 
cumulation, are  propelled  by  the  orbicular  mufcle, 
towards  its  origin  next  the  nofe,  and  to  the  inner- 
moft  part  of  the  commiffure  of  the  eyelids  ; which 
from  not  having  any  tarfus,  does  not  meet  exactly 
together.  There  a caruncle,  full  of  febaceous,  hairy 
follicles,  oblong,  and  conical  outwards,  interpofes 
itfelf  between  the  eyelids,  and  prevents  them  from 
meeting,  and  anoints  with  its  liniment  thofe  parts 
of  the  eyelids  which  have  no  Meibomian  ducts, 
Before  it,  a fmall  third  eyelid  defeends  perpendicu- 
larly, and  joins  the  true  eyelids  ; it  is  larger  in 
beafts.  At  the  beginning  of  this  fpace  interpofed 
between  the  eyelids,  in  which  the  tears  are  collect- 
ed, in  each  margin  a little  papilla  projects,  having 
one  orifice,  furrounded  by  callous  cellular  fubftance, 
and  perpetually  open,  unlefs  when  convulfively 
clofed.  This  orifice,  which  is  called  the  punctum 
lachrymale,  abforbs  the  tears  from  the  finus  in 
which  they  are  collected,  partly  by  attraction,  and 
partly  by  the  impulfe  of  the  orbicular  mufcle.  If 

thefc 


SIGHT. 


246 


Chap.  XVI. 


thefe  points  are  obllrucled,  the  tears  run  over  and 
excoriate  the  cheek. 

Dvii,  From  each  point,  a peculiar  duel,  much 
wider,  thin,  and  included  in  the  Ikin,  proceeds,  the 
one  downwards  above  the  caruncle,  and  the  other 
more  tranfverfely  inwards,  and  under  it ; which  ap- 
proach each  other,  and  are  inferted  by  two  mouths 
into  the  lachrymal  fac,  not  quite  at  the  top  ; which 
name  is  given  to  a cavity  formed  in  the  groove  of 
the  os  unguis  and  upper  jaw,  lined  firll  with  a hard 
cellular,  and  as  it  were  aponeurotic  membrane ; 
then  by  another,  red  and  pulpy,  continued  from 
the  membrane  of  the  nares,  pervious  to  the  exhaling 
moifture,  and  fomewhat  of  an  oval  figure.  From 
this  veficle  the  nafal  du(5i;  defeends  a little  backwards 
into  the  nares,  and  opens  by  an  obliquely  oblong 
aperture,  covered  by  the  lower  os  fpongiofum,  into 
their  loweft  meatus.  Through  this  the  fuperfluous 
tears  defeend  into  the  nofe,  which  they  in  part  moifi- 
en,  (ccccLxiv.)  A mufcle  is  by  fome  aferibed  to 
this  fac ; but  it  is  not  yet  fuliiciently  afeertained. 

Dviii.  The  eye,  of  a globular  fhape,  comprelied 
before,  though  not  always  in  the  fame  manner, 
longer  from  the  brain  to  the  cornea  than  from  the 
right  fide  to  the  left,  is  fituated  in  the  orbit,  \^  hich  is 
an  offeous  cavity,  almofl;  conical,  compofed  of  fe\  en 
bones,  interrupted  in  the  back  and  outer  fides  by 
larger  fififures,  and  widening  forwards,  and  by  which 
it  is  defended  on  all  fides.  But  as  this  is  larger  than 
the  eye,  it  is  filled  by  mmch  very  foft  fat,  furrounding 
the  globe  of  the  eye,  and  allowing  it  free  motion. 

Dix.  The  eye  begins  from  a nerve,  by  the  ex- 
panfion  of  whofe  coats  thofc  of  the  eye  are  formed. 
Its  origin  we  have  already  deferibed,  (ccclvii.) 
Having  paiTed  acrofs  the  crus  of  the  brain,  it  joins 
with  its  fellow  from  the  other  fide,  and  coheres 
with  it  for  a confiderabie  way,  by  much  medullary 
fubftance  ; yet  fo  that  the  right  goes  to  the  right 
eye,  and  the  left  to  the  left,  though  not  without 

fomc 


Chap.  XVI. 


SIGHT. 


247 

fome  reciprocal  intermixture  of  medulla.  The 
nerve  then  enters  the  orbit,  a little  infledled,  and  of 
a round  form,  fomewhat  comprefled ; and  is  infert- 
ed,  not  into  the  middle  of  the  globe  of  the  eye,  but 
a little  nearer  to  the  nofe. 

Dx.  The  nerve  having  reached  the  eye,  the  inner 
plate  of  its  dura  mater,  which  it  received  in  the 
opening  of  the  fphenoidal  bone,  is  detached  : or 
having  become  thicker,  is  extended  around  the 
eye,  as  its  firft  coat,  called  the  fclerotic,  or  adheres 
to  the  fclerotic,  which  perfetlly  refembles  it,  and 
always  arifes  from  it.  The  other  plate  of  the  dura 
mater,  the  external,  recedes  and  forms  the  periof- 
teum  of  the  orbit : the  pia  mater,  which  is  in  this 
nerve  very  diflin£l  and  full  of  veffels,  having  be- 
come entirely  dark  coloured  and  thin,  lines  the  in- 
lide  of  the  fclerotic.  The  remaining  medullary 
central  part  of  the  nerve,  continued  from  the  brain, 
but  divided  by  cellular  plates,  contrafts  into  a 
deprelTed  white  conical  papilla  ; which  entering 
through  the  holes  in  the  white  circle  of  the  cho- 
roid coat,  and  again  expanding,  produces  the  moft 
internal  membrane  of  the  eye,  the  retina. 

Dxi.  The  fclerotica  is  in  general  white,  furnifli- 
ed  with  few  veffels,  tough  and  compact,  refembling 
the  nature  of  Ikin,  of  a figure  very  nearly  globular, 
but  compreffed  before,  and  is  thicker  at  the  back 
part.  Before  this  coat,  which  is  perforated  by  cir- 
cular holes  in  its  forepart,  is  placed,  and  oblique- 
ly connected  v/ith  it,  a more  convex  portion  of  a 
fphere  ; pellucid,  compofed  of  many  plates,  whofe 
veffels  are  filled  with  pellucid  water,  and  are  diffi- 
cult of  demonftration,  infenfible,  and  almoft  circu- 
lar, circular  towards  the  nofe,  and  oval  towards  the 
temples  : it  is  termed  the  cornea,  and  through  it 
the  light  paffes  into  the  infide  of  the  eye.  It  readi- 
ly imbibes  and  exudes  water.  Before  the  anterior 
and  flatter  part  of  the  fclerotica,  and  before  the 
cornea,  the  conjundiva  is  detached  from  each  of 

the 


SIGHT. 


Chap.  XVI. 


248 

the  e^'^elids,  and  is  joined  to  the  fclerotica  by  pro- 
per cellular  fubftance,  which  may  be  inflated,  (d.) 
and  is  replenifhed,  partly  with  red  veffels,  and 
partly  with  their  pellucid  continuations. 

Dxii.  The  origin  of  the  choroid  coat,  is  from  the 
circumference  of  the  white  cellular  circle,  termina- 
ting the  fubflance  of  the  optic  nerve,  and  through 
whofe  numerous  foramina,  and  from  which  the  re- 
tina and  arteria  centralis  retinae  proceeds.  At  that 
place  the  choroides  adheres  to  the  iclerotic,  and  to 
the  circle  above  defcribed.  Then  it  is  expanded 
concentrically,  within  the  fclerotic,  with  v'hich  it  is 
united,  perhaps  by  fome  cellular  fiibftance,  and  by 
many  veffels,  which  come  from  it  to  the  choroides. 
Outwardly  it  is  of  a brown  colour,  but  inv^ardly  of 
a deep  ruffet  or  alraoff  black,  and  at  the  fame  time 
villous ; the  two  furfaces  are  feparable  by  macera- 
tion ; and  the  inncrmoff  may  be  diftinguiflied  by 
the  name  of  Ruyfch  ; but  it  grows  white  through 
age.  When  it  has  reached  the  beginning  of  the 
pellucid  cornea,  it  there  becomes  clofely  connected 
with  the  fclerotica,  by  much  cellular  fubftance,  hav- 
ing the  appearance  of  a white  circle,  called  orbicu- 
lus  ciliaris,  and  then  turns  off  in  another  direction  ; 
namely,  the  coat,  which  was  before  fpherically  ex- 
panded, is  now  ftrctched  under  the  arch  of  the 
cornea,  in  the  form  of  a circle,  a little  convex  ff)r- 
wards,  and  incomplete,  having  in  its  centre  a circu- 
lar foramen  called  the  pupil,  which  is  feated  nearer 
to  the  nofe,  and  is  larger  towards  the  temple.  I'he 
anterior  part  of  this  ring  is  called  the  iris  ; and  the 
back  part,  feparable  from  the  former  in  the  human 
body,  by  maceration,  in  fome  animals  even  by  the 
knife,  is,  from  the  black  pigment  with  which  it  is 
covered,  called  the  uvea.  On  the  anterior  furface 
of  the  iris  appear  numerous  radiated  and  branching 
ffreaks,  of  various  colours  in  different  people,  and 
entirely  covered  with  liocculi.  Thcfe  terminate 

on 


SIGHT. 


249 


Ghap.  XVI, 

on  this  fide  of  the  pupil  in  a ferrated  circle,  front 
which  other  fimilar  ftreaks  extend,  even  to  the 
edge  of  the  iris.  They  are  ferpentine  when  the 
pupil  is  dilated,  and  ftraight  when  it  is  contracted. 
On  the  poflerior  furface  of  the  uvea  is  much  black 
pigment ; which  being  v/aflied  off,  ftraight  radiated 
ftreaks  appear,  extending  to  the  pupil,  and  not 
flocculent.  Orbicular  fibres,  concentrical  with  the 
pupil,  I have  not  been  able  to  obferve,  either  with 
the  naked  eye,  or  with  the  microfcope,  even  in  the 
ox ; but  only  in  the  uvea,  an  internal  circle  diftin- 
guifhed  by  obfcurer  rays,  and  lefs  villous.  In  the 
human  foetus,  the  pupil  is  fliut  up,  and  the  iris  be- 
ing continued,  makes  a complete  circle.  That  part 
of  it  which  extends  acrofs  the  pupil  is  of  a vafcular 
texture. 

Dxiii.  Though  the  iris  has  little  fenfibility,  and 
is  not  endowed  with  any  mechanical  irritability  j 
yet  during  life,  in  man,  quadrupeds,  and  birds, 
the  pupil  is  contracfted  by  every  greater  degree  of 
light,  and  is  dilated  by  every  fmaller  one  ; hence 
it  is  alfo  rendered  broader  for  viewing  diftant  ob- 
jects, and  narrower  for  viewing  fucli  as  are  near. 
The  caufe  of  this  dilatation  feems  to  be  a remiffion 
of  the  powers  refifting  the  aqueous  humour  ; as 
proved  by  the  dilatation  of  the  pupil,  from  debil- 
ity, fyncope  and  death.  The  contraftion  is  lefs  un- 
derftood,  and  perhaps  only  depends  on  the  ftrong- 
er  afilux  of  humours  into  the  colouriefs  veffels  of 
the  iris,  by  which  thefe  veffels  are  extended  ; and, 
at  the  fame  time,  the  iris  is  rendered  longer,  and 
fliuts  up  the  greater  part  of  the  pupil : fo  that  this 
motion  has  fomething  in  common  with  inflamma- 
tion, as  agreeing  in  their  caufe.  In  young  people, 
the  pupil  is  more  evidently  moved  and  contracted ; 
as  the  eye  gradually  grows  callous  in  old  people,  it 
becomes  almoft  immoveable.  In  an  animal  twenty- 
three  hours  after  death,  I have  feen  the  iris  extend- 
ed by  heat  fo  as  to  ftiut  the  pupil. 


DXIV. 


SIGHT. 


Chap.  XVI. 


2.50 

Dxiv.  Behind  the  uvea,  from  the  fame  circle  in 
which  the  choroides  unites  with  the  fclerotica, 
more  externally  than  the  cornea,  thick  ftrise,  ele- 
gantly plaited,  ariling  from  the  choroides,  white, 
with  parallel  veffels  running  under  them,  with  plu- 
mous,  pendulous  extremities,  joined  to  the  loofe 
and  thin  retina,  and  every  where  covered  with  a 
good  deal  of  black  pigment,  depart,  in  the  form  of 
a.  perforated  ring,  inwards  from  the  tunica  choroi- 
dea,  and  proceed  forwards  behind  the  ciliary  circle, 
and  reft  upon  the  vitreous  humour  ; and,  laftly, 
upon  the  capfule  of  the  cryftalline  lens,  but  do  not 
adliere  to  them.  They  are  denominated  the  cil- 
iary ligaments.  The  origin  of  the  pigment  is  not 
known  ; nor  liave  the  fecreting  glands,  which  fomc 
Iiave  fuppofed,  been  found.  Among  its  ufes,  one 
feems  to  be,  to  keep  the  cryftalline  lens  firm.  In 
infants,  this  ftme  mucus,  behind  the  ciliary  pro- 
ceifes,  exprelles  the  figure  of  a radiated  flower. 

Dxv.  The  retina,  which  is  a true  continuation 
of  the  meduUa  of  the  optic  nerve,  and  therefore 
very  tender,  mucous,  and  evaporable,  is  expanded 
within  the  choroides  into  a fimilar  fphere,  concen- 
tric with  it ; and  immediately  inclofes  the  vitreous 
humour.  But  when  the  retina  has  reached  the 
ciliary  proceftes,  it  follows  their  courfe,  fupporting 
their  arteries  and  ftrise,  and  proceeds  to  the  cr)dtal- 
line  lens,  adhering  to  and  covering  its  capfule,  if 
the  obfervations  of  fomc  other  anatomifts,  as  well 
as  my  own  are  to  be  relied  on  ; for  in  quadrupeds 
this  termination  of  it  is  not  perfccUy  certain,  al- 
though in  birds  the  internal  lamina  of  the  retina, 
covered  with  the  ciliary  body,  is  evidently  contin- 
ued to  the  cryftalline  lens  ; to  the  circumference 
of  which  it  alfo  adheres  in  man.  The  fabric  of  the 
retina  is  inch,  that  externally  its  foft  and  medulla- 
ry globules  form  a thick  and  pulpy  membrane, 
within  which  radiated  fibres  proceeding  from  the 
lamina  cribrofa,  and  continued  forwards,  conftituie 

a thinnci' 


Chap. 


SIGHT. 


251 

a thinner  involucrum,  very  readily  obferved  in 
fiflres,  and  alfo  in  fome  birds  and  quadrupeds,  but 
not  in  nian,  Arterial  and  venous  veffels  with  red 
trunks,  form  a net  in  the  internal  furface  of  the  re^^ 
tina,  which  when  accurately  filled  with  coloured 
water  compofe  a membrane. 

Dxvi.  Thefe  coats,  refembling  the  coats  of  a 
bulbous  root,  are  fupported,  and  the  fpherical  fig- 
ure of  the  eye  is  preferved  by  its  humours  ; of 
which  one  is  a foiid,  another  a foft  body,  and  a 
third  truly  a liquor.  Firft,  then,  the  concave  fur- 
face  of  the.  retina  is  every  where  filled  by  the  prin- 
cipal or  vitreous  humour,  of  which  the  flructure 
confifls  of  a peculiar  thin,  pellucid,  cellular  mem- 
brane, in  whofe  cellular  intervals  is  contained  a 
very  pellucid  liquid,  very  rarely  altering  even  in 
old  age,  completely  evaporable  by  heat,  nearly  al- 
lied to  the  aqueous  humour,  and  fomewhat  denfer 
than  water.  Its  veffels,  which  are  moft  manifeft 
in  fifli,  lie  in  the  back  part,  moft  beautifully  radi- 
ated from  the  central  trunk  of  the  retina,  embrac- 
ing the  convexity  of  the  vitreous  humour  j and 
inferred  into  a circle  formed  not  far  from  the  lens 
by  other  arteries  coming  from  the  choroides,  and 
which  I have  feen  in  the  fheep.  The  vitreous  mem- 
brane, which  is  tender  confidering  its  body,  ad- 
heres to  the  lens  in  two  places,  before  and  behind ; 
fo  that  a hollow  fpace  is  intercepted  in  the  middle 
between  the  two  infections,  around  the  cryftalline 
lens.  This  fpace  is  divided  in  different  places  by 
fome  fibres.  On  its  anterior  furface  the  ftriae  of 
the  ciliary  body  imprint  their  marks. 

Dxvii.  But,  in  the  forepart  of  the  vitreous  body, 
behind  the  uvea,  there  is  an  orbicular  depreflion 
of  confiderable  depth,  into  the  cavity  of  which  the 
cryftalline  lens,  (alfo,  though  improperly,  ranked 
amongft  the  humours,)  is  received.  The  figure  of 
this  lens,  refembling  frozen  jelly,  is  compofed  of 

two 


SIGHT. 


Chap.  XVI. 


252 

two  elliptical  convex  fegments,  the  anterior  of 
which  is  flatter,  and  the  pofterior  more  gibbous. 
It  is  conftrufted  of  concentric  laminae,  connected 
by  cellular  fibres,  which  themfelves  are  compofed 
of  fibres  elegantly  difpofed  through  fine  cellular 
membrane.  Betwixt  the  plates  of  the  cryftaliine 
lens,  is  alfo  contained  a peUucid  liquor,  but  which, 
in  old  age,  naturally  acquires  a yellow  colour. 
The  innermoft  fcales  are  more  clofely  compacted  ; 
and  form  as  it  were  a harder  nucleus  ; externally 
it  adheres  fo  very  loofely  to  the  capfule,  that  when 
tlis«s  broken,  it  very  .^readily  fprings  out ; and 
f(3«ie  /^^  fay,  that  a littih.  water  is  eflufcd  around 
it.  It  i^upplied  with  an  artery  from  the  retina, 
which  perforates  the  middle  of  the  vitreous  hu- 
mour, and  enters  behind ; for  veffels  have  not 
yet  been  difeovered  on  the  anterior  furface.  The 
'vfiole  lens  is  contained  in  a ftrong,  thick,  elaftic 
capfule  of,  a pellucid  membrane,  more  firm  in  the 
forepart,  and  which  is  lined  poflerioidy  by  the  vit- 
reous tunic.  ^ 

Dxviii.  Laftly,  the  aqueous  humour,  which  is 
extremely  pellucid  and  fluid, “and  wliich  is  renew- 
ed again  if  it  be  let  out,  ^nms  in  the  fmall  trian- 
gular curvilinear  fpace  betwixt  the  uvea  and  cryf- 
taliine lens,  anchin  that  larger  fegment  of  a hollow 
fphere  which  lies  betwixt  the  iris  and  the  cornea. 
This  humour  feems  to  exhale  from  the  fmall  arte- 
ries of  the  iris,  uvea,  and  ciliary  procelTes ; being 
again  abforbed  by  the  correfponding  veins,  while 
fome  portion  of  it  is  abforbed  by  and  exhaled 
throuTn  the  cornea.  This  humour  alfo  moiftens 
the  uvea  and  capfule  of  the  lens.  About  the  be- 
ginning of  the  prefent  century,  the  fpaces  filled 
with  this  liquor  were  called  the  chambers  of  the 
eye  ; that  between  the  cornea  and  iris  the  anterior 
one,  and  that  fmall  one  between  the  furface  ot  the 
cryftaliine  lens  and  the  uvea  the  pofterior. 


DXIX.- 


Chap.  XVI. 


SIGHT. 


253 

Dxix.  The  eye,  thus  conftructed,  is  provided 
with  mufcies  externally  inferted  into  it,  by  which 
it  is  governed.  Namely,  into  the  circle  of  the 
fclerotica,  which  is  contiguous  to  the  cornea,  are 
inferted  four  flraight  mufcies,  ariling  almoft  in  one 
circle  from  the  dura  mater  of  the  optic  nerve  ; 
where,  departing  from  the  nerve,  it  coheres  with 
the  periofteum  of  the  orbit,  and  proceeding  for- 
wards with  their  bellies  round  the  bulb  of  the  eye, 
they  terminate  again  by  their  aponeurofes,  meeting 
together  in  another  circle.  Of  thefe,  the  elevator 
is  the  leall,  and  the  abductor  rather  the  longeft. 
The  office  of  each  of  thefe  mufcies  appears  very 
plainly ; fince,  being  bent  round  the  convex  bulb 
of  the  eye,  as  about  a pulley,  they  mull,  of  courfe,- 
elevate,  deprefs,  or  turn  the  eye  either  to  the  nofe 
or  to  the  temples.  Moreover,  two  of  them  acting 
together  may  move  the  eye  diagonally ; as  up- 
wards and  outwards,  upwards  and  inwards,  &c* 
Laftly,  when  all  the  four  ftraight  mufcies  contract 
together,  there  is  fcarcely  a doubt  that  they  draw 
back  the  whole  eye  within  the  head  towards  their 
origin,  and  thus  bring  the  cryltalline  lens  nearer  to 
the  retina. 

Dxx.  But  the  fabric  of  the  two  oblique  mufcies 
of  the  eye  is  more  compound.  The  upper  of  thefe, 
arifmg  together  with  the  recli,  is  long  and  flender, 
afeending  forwards  to  a notch  in  the  os  frontis, 
which  is  completed  into  a hole  by  a double  liga- 
ment, which  on  each  fide  fuftains  a cartilage,  ex- 
cavated in  the  middle,  and  almoft  quadrangulaiv 
Through  this  canal  pafles  the  tendon  of  the  obli- 
quus,  which  being  reftefted  backwards  and  out- 
wards, included  in  a capfule  of  its  own,  is  infert- 
ed into  the  globe  of  the  eye  behind  the  ftraight 
mufcies.  This  draws  the  globe  forwards,  as  if  out 
of  the  orbit,  and  inwards,  and  turns  the  pupil  in- 
wards and  downw'ards.  The  other,  the  obliquus 
minor  from  the  finus  of  the  lachrymal  foramen  in 

the 


SIGHT. 


Chap.  XVI. 


254 

the  upper  jaw,  afcends  immediately  outwards  from 
the  os  ungiiis  round  the  globe  of  the  eye,  and  is 
inferted  by  its  tendon  into  the  fclerotica  behind  the 
external  reclus  : v.Tence  it  appears  to  turn  the 
point  of  its  infertion  into  the  eye  downwards  and 
outwards ; and,  therefore,  the  oppofite  pupil  up- 
wards and  inwards. 

Dxxi.  But  there  are  other  minute  mufcular  mo- 
tions performed  in  the  eye,  which  prefuppoie  a 
knowledge  of  its  nerves.  Of  the  optic  nerve  we 
have  already  treated  (mx.  dx.)  The  fourth  pair 
goes  only  to  the  larger  oblique  mufcle,  and  the 
fixth  pair  to  the  recfus  externus.  The  third  and 
fifth  pair  produce  the  principal  nerves  in  the  eye  ; 
the  firft  or  ophthalmic  branch  of  the  fifth  fends  off 
a nerve  at  its  entrance  into  the  orbit,  to  the  eyelid 
and  lachrymal  gland,  which  joins  with  the  fecond 
branch  of  the  fifth  pair,  and  with  the  teniporal 
branch  of  the  third  of  the  fifth  pair.  On  entering 
the  orbit,  its  trunk  divides  into  two.  The  upper 
branch,  larger  and  bifid,  is  expended  on  the  fore- 
head and  eyelids : but  the  lower,  penetrating  in- 
wards above  the  optic  nerve,  fends  off  a long  ilen- 
der  filament  at  the  outer  part  of  that  nerve,  which, 
joining  with  another  filament  of  tlie  third  pair 
forms  the  ophthalmic  ganglion,  and  fends  off  one 
or  two  ciliary  nerves.  Finally,  after  having  given 
off  the  recurrent  nerve  of  the  nofe  (cccclvii.)  it 
is  then  fpent  upon  different  parts  in  the  internal 
angle  of  the  eye. 

Dxxii.  But  the  third  pair  is  of  moft  importance. 
After  giving  ofl’  a branch  upwards  to  the  Itraight 
mufcles  of  the  eye,  and  to  the  eyelids,  it  pi'oceeds 
with  its  trunk  under  the  optic  nerve,  and  at  the 
fame  time  fends  out  three  branches  to  the  inferior, 
obliquus  minor  and  interims  ; after  this,  or  before, 
from  its  trunk,  or  fometimes  from  the  branch  of 
the  obliquus  minor,  it  fends  off  another  Ihorf 
nerve,  much  thicker  than  the  root  from  the  fifth, 

(dxxi.'! 


Chap.  XVI. 


SIGHT. 


^SS 

(dxxi.)  which,  under  the  abdu<ftor  mufcle  upon 
the  optic  nerve,  forms  the  ophthalmic  ganglion, 
which  is  oval  and  conftant,  and  fometimes  arifes 
from  the  third  alone.  From  that  ganglion,  and 
fometimes  from  the  trunk  of  the  third  or  fifth,  four 
or  five  ciliary  nerves  playing  around  the  optic  nerve 
in  a flexuous  courle,  go  to  the  globe  of  the  eye, 
perforate  the  fclerotica  almoft  in  its  middle,  in 
company  with  its  longer  fmall  arteries  or  veins, 
run  ftraight  forwards  along  the  choroides,  and  vi- 
fibly  proceed  to  the  iris,  and  feemingly  to  the  cili- 
ary proceiTes.  Other  very  fmall  nerves,  originat- 
ing from  the  fame  ganglion,  remain  in  the  tunica 
fclerotica. 

Dxxiii.  The  motion  of  the  ciliary  proceffes  is 
obfcure  and  difficult  of  demonftration,  (dxiv.)  ly- 
ing incumbent  upon  the  furrows  of  the  vitreous 
membrane,  by  their  action  they  are  believed  to 
prefs  back  that  body,  fo  as  to  bring  the  lens  for- 
wards, and  remove  it  farther  from  the  retina.  But 
I have  never  feen,  in  all  the  animals  I have  differ- 
ed, any  thing  like  a mufcle  in  this  ciliary  body, 
but  only  a membrane  which  fupports  fmall  veflels. 
The  fphinder  of  the  pupil  and  conffridor  of  the 
cornea,  mentioned  by  fome  writers  of  eminence, 
and  the  moving  fibres,  which  others  have  imagined 
proper  to  the  cryffalline  lens,  are  not  confirmed  by 
anatomy,  nor  are  they  confiftent  with  the  conftant 
hardnefs  of  the  lens  and  cornea  in  moft  animals. 

Dxxiv.  The  hiftory  of  the  eye  alfo  comprehends 
its  veflels,  which  have  a moft  beautiful  fabric.  Ail 
thofe  which  belong  properly  to  the  eye  itfelf  come 
from  the  ophthalmic  artery,  a branch  of  the  inter- 
nal carotid,  (cccxvi.)  This,  creeping  under  the 
optic  nerve,  fends  off,  as  principal  branches,  the 
upper  ciliary,  one  or  more  inferior  ciliaries  ; the 
lachrymalis,  from  whence  the  nafalis  recnrrens  pof- 
terior,  and  internal  part  of  the  arch  of'the  tarfus  ; 
afterwards  the  mufcularis  inferior,  the  nafalis  re- 

currens. 


SIGHT. 


Chap.  XIV: 


currens,  anterior  and  pofterior,  the  mufculares  fu- 
periores,  and  the  palpebralis,  which,  with  the  form- 
er branch,  forms  the  arch  of  the  tarfus.  Laftly,  it 
goes  to  the  face,  nofe  and  adjacent  parts.  But  the 
ophthalmic  branches,  belonging  to  the  inner  parts 
of  the  eye,  are  called  the  ciiiaries  ; which,  arillng 
from  the  trunks  now  . mentioned,  and  playing 
around  the  optic  nerve,  in  four  or  more  branches, 
in  a ferpentine  courfc,  partly  clofe  by  the  entrance 
of  the  optic  nerve,  go  to  the  choroides  with  forty 
or  more  branches,  and  make  upon  its  external  fur- 
face,  ramifications  divided  at  acute  angles,  which 
proceed  forwards  to  the  circle  of  the  uvea. 

Dxxv.  But  molt  of  the  fmall  arteries  of  the  tu- 
nica choroides  gradually  incline  towards  the  inte- 
rior parts  of  the  eye  ; and,  being  covered  with  a 
kind  of  cellular  down,  go  to  the  ciliary  procefles, 
along  each  of  which  two  fmall  arteries  run,  giving 
off  on  every  fide,  vafcular  flocculi,  and  inofculating 
at  their  apex. 

Dxxvi.  Other  fmall  arteries  alfo,  likewife  arifing 
from  the  ciliary  ones,  but  few  in  number,  moll 
commonly  two,  go  to  the  place,  from  which  the 
uvea  originates.  There,  fpreading  in  various  di- 
reclions,  they  furround  the  root  of  the  uvea  with 
their  branches,  and  join  to  form  a circle,  into 
which  the  anterior  ciliaries  inofculate  ; which  are 
fmall  arteries  arifing  from  the  mufcular  branches  of 
the  ophthalmic ; and  are  inferred  into  the  circle 
generally  by  twelve  fmall  trunks,  near  the  origin 
of  the  cornea.  From  that  circle,  and  likewife  from 
the  above  mentioned  anterior  ciliaiy  arteries,  with- 
out the  intervention  of  the  circle,  llraight,  branch- 
ed veflTels,  arc  diftributed,  both  on  the  iris,  and  on 
the  uvea  5 the  former  full  of  a blue  or  dark  colour- 
«d  fiuid  ; and  the  latter  naturally  white,  but  cov- 
ered with  a good  deal  of  a black  paint.  In  the 
uvea,  at  fome  diftance  from  the  pupil,  they  fre- 
quently form  an  imperfect  circle. 


DXXVIT. 


SIGHT. 


Chap.  XVI. 


257 


Dxxvii.  But  from  the  fame  ophthalmic  artery, 
from  its  trunk,  or  from  the  lachrymal  branch,  or 
from  one  of  the  ciliaries,  one  or  more  branches  en- 
ter into  the  optic  nerve  ; the  principal,  the  central 
artery  of  the  retina,  penetrates  into  the  medulla  of 
the  nerve,  and  palling  through  the  apex  of  the  pa- 
pilla, (dx.)  enters  the  centre  of  the  retina ; from 
thence  it  fpreads  every  way  through  the  retina-  it- 
felf,  by  fo  many  branches,  when  traced  by  a Ikilful 
anatomill  j that  that  vafcular  network  has  been  taken 
for  a peculiar  membrane.  Sometimes  a fmall  branch 
goes  along  the  centre  of  the  nerve  to  the  retina,  and 
is  in  like  manner  ramified  through  it.  From  com- 
parative anatomy,  it  is  certain,  that  from  thefe 
branches  the  vafcular  branches  of  the  vitreous  tu- 
nic are  produced,  as  well  as  the  pofterior  artery  of 
the  lens.  The  moft  internal  of  thefe  arteries,  is  the 
celebrated  porus  opticus  of  the  ancients. 

Dxxviii.  The  veins  of  the  eye,  in  general,  arlfe 
from  the  ophthalmic  vein,  which  on  the  one  fide 
comes  from  the  facial  vein,  entering  the  orbit  ; 
and  on  the  other,  is  inferted  into  the  cavernous 
finus.  The  internal  veins  of  the  eye  perforate 
the  middle  of  the  fclerotica,  with  fewer  and  larger 
trunks  than  the  arteries,  and  form  larger  and  more 
anterior  reticulations,  of  a roundifli  figure,  which 
commonly  occupy  the  middle  of  the  tunica  cho- 
roides ; fome,  which  are  long,  are  continued  to  the 
origin  of  the  uvea  : others  anterior,  fimilar  to  the 
arteries  ; and  another,  the  centralis  nervi  optici,  cor- 
refponding  with  the  artery,  goes  to  the  retina.  The 
pellucid  veffels  do  not  differ  from  the  fanguiferous. 
Lymphatic  veffels  are  faid  to  have  been  feen  in  the 
retina ; but  the  obfervation  has  not  been  fufiiciently 
repeated. 

Dxxix.  So  far  with  refpecL  to  the  anatomy ; but 
the  aftion  of  the  eye  is  entirely  elucidated  by  phy- 
fical  experiments,  from  which  it  has  been  afcer- 
tained,  in  the  moft  incontrovertible  manner,  except 
S a few 


SIGHT, 


Chap.  XVI. 


25S 

a few  doubtful  points.  Light  is  the  fame  matter 
with  heat,  or  very  nearly  the  fame,  poffelling  ex- 
treme fluidity  and  fubtiity,  penetrating  through 
all  bodies,  very  rigid,  not  exhaufted  by  any  dif- 
tance  of  its  paffage,  and  moving  with  exceffive  ve- 
locity, fo  as  to  arrive  at  the  earth  from  the  fun  in 
eight  minutes  and  thirteen  feconds.  Light  in  our 
planet  proceeds  either  from  the  fun,  which  feems 
to  have  the  power  of  arranging  in  ftraight  lines,  the 
matter  of  light,  otherwife  confufedly  fcattered  ; 
or  from  fome  other  lucid  point.  From  it,  as  from 
a centre,  the  light  is  diftributcd  like  rays,  to  all  parts 
of  the  fphere,  fo  as  to  fall  upon  the  furfaces  of  all 
bodies  ; from  whence  again  it  is  reflected,  and  im- 
pinges on  the  eye,  at  angles  equal  to  the  angle  of 
incidence,  and  renders  the  bodies,  from  which  it 
comes,  coloured  and  vifble. 

Dxxx.  It  is  afcertained,  from  experiments,  that 
light  is  compofed  of  rays  in  right  lines,  almofl  vdth- 
cut  any  phyf  cal  breadth  ; and  yet,  each  of  which 
may  be  feparated  into  feven  more  minute,  perma- 
nent and  immutable  rays.  The  known  properties 
of  thefe  rays  are.  that  all  of  theiUj  conjoined  togeth- 
er, confiitute  a white  beam  ; but  when  refracted, 
and  feparated  by  the  minute  furfaces  of  bodies, 
they  are  fubdivided  into  red  rays,  which  are  the 
molt  conflant,  hard,  and  leaft  refrangible  ; and  af- 
terwards into  orange,  yellow,  green,  blue,  indigo, 
and  violet ; which  are  always  weaker  and  more  rc- 
franmbie,  as  thev  are  farther  diftant  in  order  from 
the  red  rays.  Shade  arifes  from  a deficiency  of  re- 
flected rays.  Colours  are  compounded  of  fltade 
united  with  various  rays. 

Dxxxi.  The  peculiar  colours  of  bodies  arife  from 
the  minute  furfaces  of  their  folid  particles,  by  which 
their  pores  are  limited,  which  refraCt  the  rays  of 
light,  according  to  the  difference  of  their  thicknefs, 
reflecting  one  kind  of  ra.ys  moft  copioufly,  and  in  a 
great  meafure  fuffocating  by  repeated  internal  refrac- 
tions, the  others  admitted  into  their  fubftance:  fothat 


SIGHT; 


Ghap.  xvi. 


259 


the  thickeft  and  denfeft  particles  reflect  a white  col- 
our ; the  next  red ; and  the  thihneft  violet.  Bodies 
are  opaque,  which  retain  all  the  rays,  and  tranfmit 
none,  from  the  largenefs  of  their  pores,  to  the  tides 
of  which  the  light  is  attracted ; and  which  are  fill- 
ed with  fome  matter  that  has  a power  of  refraction, 
different  from  that  of  the  particles  of  the  body. 
Thefe  principles  we  embrace,  till  a new  theory, 
which  afcribes  the  diverfity  of  colours  to  vibra- 
tions of  different  celerities,  ihall  be  better  eftablifh- 
ed  ; for  it  is  not  our  bufinefs  to  afcertain  thefe  mat- 
ters. 

Dxxxii.  Thefe  rays,  when  they  fall  obliquely  up- 
on liquors  of  various  denfities,  in  palling  through 
them,  varioufly  recede  from,  or  incline  towards  the 
perpendicular  : this  is  called  refradlion.  In  gen- 
eral, the  denfer  the  medium^  the  more  are  the  rays 
bent  towards  the  perpendicular ; excepting  only  in- 
flammable liquors,  which,  by  a peculiar  property, 
attradl  the  rays  more  to  the  perpendicular,  than  in 
proportion  to  their  denfity.  The  proportions  of 
the  angles  of  incidence  to  thofe  of  refraftion,  are 
conftant ; fo  that  the  fine  of  the  angle  of  refrac- 
tion of  rays  palling  from  air  into  water,  is  to  the 
fine  of  the  angle  of  incidence,  as  3 to  4 : and  of 
rays,  palling  from  air  into  glafs,  the  fine  of  the  in- 
cidence is  to  that  of  refradion,  as  1 7 to  1 1 5 and 
from  water  into  glafs,  as  5 1 to  44. 

Dxxxiii.  Rays,  which  come  through  the  air  with 
but  little  divergency,  as  thofe  of  the  fun  on  ac- 
count of  its  immenfe  diftance  ; or  as,  in  general, 
any  rays  that  come  from  a diftance  of  above  100 
feet,  when  they  fall  upon  a body,  fpherically  con- 
vex, and  denfer  than  the  air,  at  a large  angle,  as  at 
48  i degrees,  are  refle<fted,  and  do  not  penetrate  it. 
If  the  angles  are  fmaller,  they  penetrate  the  refra<ft-i 
ing  medium,  and  are  refrafted  in  it,  fo  as  to  meet 
together  in  one  point,  which  is  called  their  focus^ 
This  point  lies  in  the  axis,  or  in  the  ray,  falling 
s 2 perpendicularly 


SIGHT. 


Chap.  XVl. 


i6o 

perpendicularly  on  the  furface,  and  therefore  not 
inhered ; and  in  a fpherkal  globule  of  water,  the 
focus  of  rays  coming  from  the  atmofphere,  is  at 
the  diilance  of  one  iemidiameter  from  the  fphere  j 
and  in  a fphere  of  glafs,  a fourth  part  of  the  diam- 
eter, and  in  a convex  lens  of  glafs,  that  is,  a part  of 
a fphere  not  lefs  than  thirty  degrees,  and  equally 
convex,  it  is  alfo  one  femidiameter  ; but  fo  that  the 
rays  meet,  not  in  a point,  but  in  a little  circle. 

Dxxxiv.  Therefore  the  rays  of  light,  whether  di- 
rect or  reflected,  fall  in  fuch  a manner  upon  the 
cornea  of  the  eye,  as  to  form  a very  acute  cone, 
from  the  lucid  point  to  the  furface  of  the  mem- 
brane : the  balls  of  which  is  the  furface  of  the  cor- 
nea, and  the  apex  the  radiant  point ; yet  fo,  that 
the  rays  of  the  cone  may  be  confidered  parallel, 
without  any  fenfible  error.  Of  thefe  rays,  all  thofe 
which  fall  upon  the  cornea  at  a greater  angle  than 
forty  degrees,  are  reflecled  from  the  cornea  with-^ 
out  penetrating  its  furface.  Others  which  enter 
the  cornea,  but  ftill  at  large  angles,  fall  in  betwixt 
the  uvea  and  fides  of  the  cryltalline  lens,  and  are 
I'ufi'ocated  in  the  black  paint  that  lines  the  uvea, 
(dxii.)  and  the  ciliary  procefles,  (dxiv.)  and  thofe 
rays  only  fall  upon  the  furface  of  the  lens,  which 
enter  the  cornea  at  fmall  angles,  not  much  diHant 
ii'om  the  perpendicular,  or  at  about  twenty-eight 
degrees.  By  this  means,  all  thofe  rays  are  exclud- 
ed, which  the  refracting  power  of  the  humours  in 
the  eye  could  not  have  been  able  to  collect  into  one 
point  of  the  retina ; and  which,  therefore,  would 
have  painted  the  image  on  the  retina  too  broad  and 
confufed. 

Dxxxv.  Thofe  rays,  therefore,  coming  from  the 
air,  which  is  fo  thin,  and  palling  through  the  cor- 
nea, wliich  is  the  fegment  of  a fphere,  thick,  denfer 
than  water,  and  therefore  almoft  a fourth  part  more 
refracting,  are  remarkably  inclined  towards  the 
perpendicular.  By  the  aqueous  humour,  which  is 

linalJ 


Chap.  XVI. 


SIGHT. 


261 


fmall  in  quantity,  and  almofl  like  water,  but  rather 
lighter,  they  are  not  altered,  and  fall  upon  the  fur- 
face  of  the  tranfparent  lens,  before  they  have  form- 
ed a focus,  becaufe  of  its  nearnefs,  nearly  parallel, 
or  rather  converging  ; becaufe  their  divergency 
was  abundantly  corre6led  by  the  refrading  power 
of  the  cornea.  Moreover,  the  cornea  being  convex, 
and  more  prominent  than  the  hemifphere  of  the 
fclerotica,  receives  and  collects  a greater  number  of 
rays  than  if  its  furface  were  flatter,  and  therefore 
fmaller. 

Dxxxvi.  That  the  refradUng  power  of  the  cryf- 
talline  lens,  exceeds  that  of  water,  may  be  under., 
flood  from  its  hardnefs  and  weight,  although  we 
have  no  fufficiently  certain  meafure.  In  this  lens, 
therefore,  and  more  efpecially  in  its  poflerior  very 
convex  furface,  the  rays  converge  very  much,  and 
pafs  thence  into  the  vitreous  body. 

Dxxxviii.  This  fubflance  is  denfer  than  water, 
fince  it  finks  in  it ; but  rarer  than  the  cryflaliine 
lens  ; bends  the  rays  a little  more  gently  towards 
the  perpendicular,  till  at  length  the  rays,  coming 
from  a point  of  diflinft  vifion,  are  concentrated  in- 
to the  fmalleft  poflible  point  of  the  retina,  where 
they  paint  an  image  of  the  obje6l  from  which  they 
come  ; but  inverted,  on  account  of  the  neceffary 
decufl'ations,  The  manner  in  which  the  images  of 
objects  are  thus  painted,  may  be  feen  in  an  artifi- 
cial eye,  or  in  a natural  eye,  when  the  back  part  of 
the  fclerotica  is  removed.  But  the  image  is  paint- 
ed on  the  outer  fide  of  the  entrance  of  the  optic 
nerve,  at  the  termination  of  the  axis  of  vifion, 
which  is  not  limited  to  a mere  point,  but  has  fome 
breadth  ; fince  we  fee  many  objedls  at  once,  v/hofe 
images  mufl  be  reprefented  in  different  points. 
Vifion  is  there  moft  diflinft,  becaiafe  the  rays  ar- 
rive thither  nearly  perpendicular.  But  frequently 
it  does  not  fill  on  the  fame  place  in  both  eyes  of 
the  fame  individual.  When  the  lens  is  deftroyed. 


SIGHT. 


262 


Chap.  X\T. 


the  vitreous  humour  alone  collecls  the  rays,  though 
lefs  powerfully. 

Dxxxix.  Is  it  entirely  falfe  that  the  objecl  is 
painted  on  the  retina  ? Is  the  picture  reprefented 
on  the  choroides  ? Is  this  new  opinion  confirmed 
by  the  experiment,  by  which  it  appears,  that  the 
place  where  the  optic  nerve  enters  is  infenfible  ? 
and  which  is  thus  explained,  that  there  is  in  that 
place  no  choroides  but  only  the  bare  retina,  and 
that  therefore,  it  does  not  poffefs  vifion.  But  this 
is  repugnant  to  a very  well  known  obfervation, 
that  the  retina  is  a mofi:  fenfible  nervous  medulla  ; 
and  that  the  choroides  almoft  entirely  confifts  of  a 
few  fmaU  nerves,  and  of  veflels  which  are  moft  cer- 
tainly blind.  This  is  likewife  contradicted  by  the 
very  great  variety  of  the  choroides  in  animals  ; by 
the  equally  great  uniformity  of  the  retina  ; and  by 
the  black  fpots,  which,  even  in  man,  obfeure  the 
exterior  furface  of  the  retina.  But,  by  this  experi- 
ment, we  perceive  the  reafon  why  the  optic  nerve 
is  not  inferred  into  the  axis  of  the  eye,  but  to- 
wards one  fide.  For  thus,  except  only  in  the 
fingle  cafe,  where  an  impediment  is  fituated  in  the 
point  of  interfeftion  of  lines  drawn  through  the 
centre  of  the  optic  nerves,  the  one  eye  fees  and 
afiiids  that  v/hofe  blind  portion  is  directed  to  the 
object. 

DXL.  But  fince  the  ncceflary  functions  of  human 
life  require  that  a diftincl:  object  be  painted  upon 
the  retina,  not  only  by  the  rays  which  come  from 
one  certain  diftance,  but  likewdfe  that  rays  w'hich 
come  from  various  and  very  dififerent  fituations, 
more  or  lefs  difiant,  fliould  excite  a diftinct  idea  of 
the  objeft  from  which  they  come : therefore,  it  is 
believed,  that  the  necefiary  change  is  produced  in 
the  eye  by  proper  means.  Some  celebrated  anato- 
mifts  have  fuppofed  the  lens  moveable  by  the  pow- 
ers before  mentioned,  (nxix.  nxxiii.)  They  afl'ert 
this  art  of  changing  the  eye  is  learned  by  experi- 
ence, 


Chap.  XVI. 


SIGHT. 


263 

ence,  and  is  not  poITeffed  by  thofe  on  whom  the 
operation  of  couching  the  catarafl  has  been  lately 
performed.  Alfo  in  an  artificial  eye,  the  advantages 
and  neceffity  of  this  motion,  it  is  faid,  may  be  plain- 
Jy  perceived.  Therefore,  too  great  a divergency  of 
the  rays,  as  in  thofe  which  come  from  objefls  very 
clofe  to  the  eye,  is  corre6led  by  the  removal  of  the 
lens  farther  from  the  retina,  by  which  means  the 
focus,  which  is  more  diftant,  on  account  of  the  di- 
vergence of  the  rays,  falls  upon  the  retina  itfelf, 
which  would  otherwife  have  fallen  behind  the  reti^ 
na ; for  the  refrafting  power  of  the  eye  being  fupr 
pofed  to  be  fuch,  as  will  caufe  the  focus  of  rays 
coming  from  the  diftance  of  three  feet,  to  fall  exacts 
ly  upon  the  retina,  it  will  not  be  able  to  collect  to- 
gether into  the  fame  point,  rays  which  come  from 
the  diftance  of  three  inches  ; and  the  more  diverg.- 
ing  rays,  when  not  collefted  by  more  powerful 
means,  will  be  too  late  of  uniting. 

DXLi.  But  thofe  rays,  which  come  from  very 
remote  fituations,  and  may  be  therefore  reckoned 
parallel,  would  meet  in  the  vitreous  humour  before 
they  reached  the  retina ; and  would  again  feparate 
as  rays  from  the  point  of  concourfe,  as  if  from  a 
lucid  point : it  is  therefore  believed,  that  the  pow- 
ers, (dxxiii.)  remove  the  cryftalline  lens  from  the 
cornea,  and  carry  it  nearer  to  the  retina,  that  the 
rays  may  meet  at  a greater  diftance  from  the  lens, 
and  that  that  diftance  may  be  accommodated  fo  as 
to  fall  upon  the  retina.  For  an  eye,  that  will  col- 
le<ft  the  rays  coming  from  a diftance  of  feven  inch- 
es, on  the  retina,  will  collect  thofe  which  come  from 
a diftance  of  three  feet  too  foon,  and  before  they 
reach  the  retina.  So  that  it  feems  perfectly  necef- 
fary  for  the  eye  to  be  made  thus  changeable,  fince 
we  fee  diftinftly  at  various  diftances.  The  point 
of  diftinct  vifion  is  that  in  which  the  given  object 
is  painted  on  the  retina  in  the  leaft  fpace  poflible. 
The  powers  colleding  the  rays,  are  often  very  dif- 
ferent 


SIGHT. 


Chap.  XVT. 


264 

ferent  in  the  two  eyes  of  the  fame  perfon,  fo  that 
the  one  eye  is  rather  long  fighted,  and  the  other 
Ihort  fighted. 

DXLii.  Thefe  and  other  fimllar  opinions,  com- 
naonly  received,  are  taught,  more  efpecially  by  the 
mathematical  phyficians,  who  more  obvioufly  per- 
ceive the  neceflitv  of  thefe  changes.  Yet  there  is 
no  power  in  the  human  eye  which  can  either  moA^e 
the  cryftalline  humour  from  its  place,  or  comprefs 
it.  And  v/e  do  not  perceive  this  faculty  in  our- 
felves  : for  we  m.ove  a book,  which  by  being  too 
far  off  we  fee  confiifedly.  nearer  to  our  eyes,  which 
we  would  not  do,  if  by  an  internal  change  in  the 
eye  we  could  correct  the  fault  of  the  diftance  : and, 
through  a frnall  hole,  we  perceive  an  objecl:’only 
fingle  in  the  point  of  difiincf  vifion,  but  double  in 
every  other.  Perhaps  the  contradlion  of  the  pupil 
may  have  fome  effect  in  enabling  us  to  fee  near  ob- 
jects more  dictinclly. 

DXLiii.  But  this  adaptation  is  not  fufficient  in 
all  perfons  : for  there  are,  and  now  more  com- 
monly than  formerly,  perfons  leading  a fedentary 
life,  and  occupied  with  the  obfervation  of  very 
minute  obje(fts,  in  vdiom  the  cornea  is  more  con- 
vex and  denfe  ; the  cryftalline  lens  more  convex 
and  folid  ; the  eye  itlelf,  by  the  weight  of  the 
humours,  more  elongated  ; and  the  reft  of  the  hu- 
mours themfeives  probably  more  denfe  ; and  in 
whofe  eyes  one,  or  levcrsJ,  or  all  of  thefe  difeafes 
occur.  In  thefe  perfons,  the  iris  is  fenfible  in  a 
fmall  light  ; and  therefore  from  their  winking, 
they  are  denominated  myopes.  In  thefe,  the  point 
of  diftinCL  vifion  is  very  near  to  the  eye,  from  one 
to  feven  inches  from  the  eye  j they  fee  remoter  ob- 
jeffs  obfcurely,  without  being  able  to  diftinguilh 
their  parts.  The  reafon  of  this  is  evident ; iince, 
from  the  caufes  jufi  mentioned,  the  too  great  re- 
frafling  power  of  the  humours,  caufes  the  diftant 
and  confequently  parallel  rays  to  m.eet  before  the 

retina  ; 


SIGHT. 


Chap.  XVI. 


265 


retina ; and  therefore  diverging  again  from  their 
focus,  they  faU  upon  the  retina  in  many  points. 
Thus  alfo  to  a found  eye,  the  perception  of  near 
objeds  is  confufed  ; becaufe  the  rays  coming  from 
thefe  are  fpread  all  over  the  retina,  without  being 
coUefted. 

DXLiv.  The  remedy,  in  the  commencement  of 
this  difeafe,  is  to  view  diftant  places,  to  abftain 
from  minute  obje6ts,  and  concave  glaffes,  and  to 
look  through  a fmall  aperture,  by  which  the  light 
is  weakened.  V/hen  the  diforder  is  confirmed,  it 
is  alleviated  by  the  ufe  of  a concave  lens,  which 
diminiflies  the  refrafting  power  in  the  humours, 
cornea,  and  cryftalline  lens,  in  proportion  to  its 
concavity  ; and  thus  removes  the  focus  of  diftant 
objeds  farther  from  the  cornea,  fo  as  to  fall  upon 
the  retina.  This  glafs  ought  to  be  a portion  of  a 
fphere,  whofe  diameter  is  equal  to  the  diftance  of 
diftind  vifion  by  the  naked  eye,  fquared  by  the 
diftance  of  diftind  vifion  in  the  eye  furniihed  with 
a glafs,  and  divided  by  the  difference  betwixt 
them.  Short  fighted  people  may  hope  for  fome 
relief  from  the  progrefs  of  life ; for  children  are 
almoft  all  myopes : but,  as  they  grow  older,  the 
eye  becomes  flatter  from  the  ftrength  of  the  folids, 
it  becomes  ftiorter,  and  the  converging  powers,  of 
the  lens  and  cornea  are  diminiftied. 

DXLV.  Another  defed,  the  oppofite  of  the  form- 
er, troubles  people  who  are  in  the  habit  of  look- 
ing much  at  very  diftant  objeds,  and  is  efpecially 
frequent  and  incurable  in  old  people.  In  it,  the 
cornea  and  cryftalline  lens  are  flatter,  and  the  hu- 
mours of  the  eye  have  a lefs  refrading  power. 
Hence  near  objeds,  whofe  rays  fall  very  diverging 
upon  the  cornea,  appear  to  them  confufed ; becaufe 
the  converging  powers  of  the  eye  are  not  fufiicient 
to  colled  the  rays  into  a focus  upon  the  retina,  and 
the  rays  arrive  at  it  fcattered,  and  have  their  focus 
behind  the  eye  ; hence  their  vifion  is  confufed. 

The 


SIGHT. 


266 


Chap.  XVf. 


The  point  of  diftincf  vifion  among  prefbyopi,  is 
from  fifteen  inches  to  three  feet. 

DXLvi.  Such  perfons  are,  in  fome  meafure,  re- 
lieved by'looking  through  black  tubes,  by  the  ufe 
of  which  the  retina  grows  tenderer,  and  the  rays 
come  to  the  eye  in  a parallel  direction.  The  re- 
medy here  is  a convex  lens  of  glafs,  which  may 
caufe  the  rays  to  converge,  fo  as  to  meet  fooner  in 
a focus,  and  upon  the  retina.  The  diameter  of  the 
fphere,  of  which  fuch  a lens  ought  to  be  a portion, 
is  exactly  as  before  (dxliv.)  There  is  no  hope 
from  age,  which  increafes  the  malady. 

DXLvii.  The  medium  betwixt  the  fhort  and 
long  lighted  eye  is  the  belt,  with  which  a perfon 
can  fee  diftinctly  objects  that  are  both  tolerably 
near  and  tolerably  remote,  and  therefore  may  af. 
fume  the  properties  both  of  the  myopes  and  pref- 
byopi ; of  this  kind  we  reckon  an  eye  that  is  able 
to  read  diftinctly  at  the  diftance  of  one  foot.  But 
other  conditions  are  neceflary,  fuch  as  perfect  clear- 
nefs  of  the  humours ; great  mobility  of  the  eyes  ; 
fenfibility  of  the  pupil ; and  a retina,  neither  too 
fenfible  nor  callous. 

DXLviii.  But  by  means  of  the  eye,  the  mind  does 
not  receive  a ftmple  reprefentation  of  the  image 
of  the  object  on  the  retina,  which  is  transferred  to 
the  feat  of  the  foul ; but  many  things  are  added 
from  experience, f*.  w'hich  the  eye  does  not  really 
fee,  and  other  things  are  interpreted  differently 
by  the  mind,  from  what  they  arp  reprefented  by 
the  eyes.  And,  firft,  the  magnitude  of  an  objed 
is  judged  of  by  the  optical  angle  intercepted  be- 
tween the  radiating  object  as  the  vertical  point, 
and  the  cornea  as  the  bafe.  From  hence,  things 
very  near  feem  large,  and  remote  objects  fmall. 
To  this  may  be  referred  the  power  of  the  micro- 
fcope,  by  which  objects  are  made  to  appear  to  us 
fo  much  larger,  as  the  diftance  of  the  focus  of  the 
glafs  lens  is  left  than  the  diftance  of  diftincft  vifion  ; 


SIGHT. 


Chap.  XVI, 


267 


and,  in  reality,  they  do  not  appear  larger,  but  only 
more  diftin£t  and  lucid  ; whence  the  mind  judges 
them  to  be  nearer. 

Dxnix.  In  the  fame  external  light,  the  ftrength 
of  illumination  depends  upon  the  fame  angle,  and 
upon  the  number  of  rays,  joined  with  the  fmallnefs 
of  the  point  which  they  affeft  in  the  retina  ; near 
obiects  therefore  appear  brighter,  and  diftant  ob- 
ieds  more  obfcure  ; or  if  remote  objefls  appear 
bright  by  their  own  light,  the  mind  reprefents  them 
as  large,  or  near,  or  both. 

DL.  The  place  of  a vilible  objefl  is  eftimated  by 
one  eye,  to  be  in  a line  comprehended  by  two 
other  ftraight  lines  drawn  to  the  extremities  of  the 
body.  If  the  fame  body  is  beheld  with  both  eyes, 
it  will  then  feem  to  be  in  the  concourfe  of  two 
lines  drawn  through  the  axis  of  each  eye  to  the 
pbjeft. 

DLi.  We  do  not  fee  diftance  ; and  a blind  man, 
who  has  never  feen,  on  acquiring  the  ufe  of  fight, 
imagines  every  thing  he  fees  to  touch  him.  After 
much  experience,  we  at  laft  make  conjectures  about 
diftances,  though  always  fallacious  : but  we  judge 
of  them  both  from  the  diminution  of  the  known 
bulk  of  the  body,  and  from  the  diminifhed  ftrength 
of  the  light,  and  faint  image  of  the  objeft  whofe 
parts  we  diftinguifh  lefs  evidently,  and  from  the 
number  of  bodies  interpofed,  v/hofe  diftance  is 
known  to  us. 

DLii.  Convexity  is  not  feen  ; but  from  expe- 
rience, a body  is  reckoned  convex,  after  we  have 
learned,  that  a body,  which  is  convex  to  the  feel- 
ing, caufes . light  and  fhadow  to  be  difpofed  in  a 
certain  manner.  It  is  convex  if  the  lhade  be  in 
the  fide  correfponding  to  the  left  hand,  and  con- 
cave if  in  the  right.  Hence  it  is,  that  microfcopes 
frequently  pervert  the  judgment,  by  tranfpofing  or 
changing  the  fhadows.  The  fame  alfo  happens  in 
that  phenomenon  .which  is  not  yet  fufSciently  un- 

derftood. 


268 


SIGHT. 


Chap.  XVI. 


derftood,  by  which  the  concave  parts  of  a feal  are 
made  to  feem  convex,  and  the  contrary. 

DLiii.  The  parts  of  a vifible  object  are  judged 
by  the  mind  to  have  the  fame  fituation  which  they 
have  in  the  object,  and  not  inverted  as  they  are  on 
the  retina.  The  mind  poffeffes  this  power  of  cor- 
rection, previous  to  experience  in  men  who  have 
been  born  blind,  and  in  animals  at  birth,  as  appears 
by  indubitable  experiments  upon  men,  who  had 
been  blind  from  birth,  and  acquired  the  power  of 
viiion  fuddenly  by  the  operation  of  couching. 

DLiv.  Another  falfe  perception  of  the  mind  a- 
rifes  from  this  circumftance,  that  external  fenfa- 
tions  conveyed  to  the  feat  of  the  foul  by  the  eyes, 
are  reprefented  during  almoft  the  fpace  of  a fecond 
of  a minute,  to  the  mind  as  objeCts  really  pre- 
fent.  Hence  proceeds  the  idea  of  a fiery  circle 
from  the  circumrotation  of  a lucid  body  ; and 
hence  the  continuance  of  the  image  of  the  fun,  and 
fometimes  alfo  of  opaque  bodies. 

DLv.  Do  wc  perceive  only  that  objeCl  diftincUy 
which  is  directly  before  that  part  of  the  retina 
which  fees  moft  diftincUy  ? And  does  the  mind 
perfuade  itfelf,  that  it  fees  many  objeCts  at  a time, 
partly  from  the  duration  of  the  ideas,  and  partly 
from  the  quicknefs  of  the  motions  in  the  eye  ? Con- 
cerning  perfectly  diftinCt  Aufion,  this  is  moft  cer- 
tain ; but  we  can  hardly  affirm  it  of  that  which  is 
lefs  diftinCt.  Why  do  we  fee  only  one  objeCt  with 
two  eyes  ? Becaufe  the  fenfation  is  fingle,  and  with- 
out difference,  when  we  have  ftmilar  impreffions 
of  two  objects.  For,  even  without  the  decuffation 
of  the  optic  nerves,  infects  who  have  numerous 
eyes  perceive  objects  fingle.  Hence  the  images  of 
two  objects  excite  only  one  fenfation  in  the  mind, 
when  they  fall  upon  the  fame  point  of  the  retina  ; 
but  two  fenfations  arife  from  one  object,  when  the 
images  fall  upon  difterent  parts  of  the  retina  of 
qach  eye.  Whence  proceed  diurnal  and  nocturnal 

blindnefs  ? 


Chap.  XVII.  INTERNAL  SENSES. 


d6g 

blindnefs  ? The  latter  is  common  to  many  nations 
living  in  the  very  warm  climates,  and  under  the 
vertical  fun,  and  to  old  men.  The  former  happens 
in  inflamed  eyes,  and  in  young  men  of  a hot  tem- 
perament, and  hence  furnifhed  with  eyes  vaftly  fen- 
Able.  For  great  fenfibility  of  the  retina  produces 
diurnal  blindnefs  ; infenfibility  produces  nodurnal 
blindnefs.  How  do  animals  fee  in  the  dark  ? From 
a large  dilatable  pupil,  tender  retina,  and  refulgent 
and  very  lucid  choroides.  Why  do  we  become 
blind  when  brought  out  of  a ftrong  light  into  a 
weak  one  ? Becaufe  the  optic  nerve,  having  fuffer- 
ed  the  action  of  ftronger  caufes,  is  not  affedted  by 
weaker  ones.  Why  is  the  fudden  tranflation  from 
a dark  place  into  the  light  painful  ? Becaufe  the 
pupil,  being  widely  dilated,  fuddenly  admits  una- 
^Wares  too  great  a quantity  of  light,  and  the  retina 
having  been  but  flightly  affedbed  by  the  weak  light, 
now  feels  the  ftronger  impreffions  very  acutely. 
Do  we  fee  with  one  eye,  or  with  both  ? Moft  fre- 
quently with  one,  efpecially  and  generally  the  right 
eye : but  by  the  afliftance  of  the  other,  we  fee  more 
objedts,  and  more  plainly  j and  we  alfo  diftinguifti 
more  points  of  the  fame  objedb,  and  judge  better 
of  diftances. 


CHAP.  XVII. 

INTERNAL  SENSES. 

DLvi.  have  confidered  the  fenfes  apart. 

V V It  is  common  to  them  all,  that  the 
medulla  of  the  tender  and  pulpy  nerve,  being  af- 
fedbed  by  external  objedts,  tranfmits  fome  change 
by  the  nervous  fpirits,  to  that  part  of  the  brain 
where  the  fibres  of  the  nerve  afledbed  firft  arife 
from  the  arteries  of  the  brain  (ccclxxxii.)  We 
know  nothing  more,  than  that  new  thoughts  are 

excited 


INTERNAL  SENSES.  CriAp.  XVII. 


57  e> 

excited  in  the  mind,  as  often  as  a change  of  this 
kind,  originating  in  any  organ  of  fenfe,  is  tranfmit- 
ted  to  the  origin  of  the  nerve  affefted.  For  this 
perception  is  not  an  adual  reprefentation  of  the  ob- 
ject, by  which  the  fentient  nerve  is  affected.  The 
idea  of  rednefs  has  nothing  in  common  with  ravs 
little  refrangible,  and  feparated  from  the  feven  por- 
tions of  the  total  ray  ; and  much  lefs  is  it  confiftent 
with  optical  principles,  for  an  image  painted  by 
rays  upon  a foft  wEite  nerve,  to  be  conveyed  for  a 
long  way,  in  perfect  darknefs,  through  a complete- 
ly opaque  body,  to  the  origin  of  the  thalami  optici. 
There  is  nothing  in  the  pain  of  burning  that  can 
reprefent  to  the  mind  the  violent  motion  of  a fwift 
and  fubtile  matter,  by  W'hich  the  particles  of  the 
nerves  are  removed  from  mutual  contact.  There  is 
nothing  in  the  idea  of  a lharp  found  from  a cord^ 
of  a certain  length,  that  can  inform  the  mind  that 
the  faid  cord  vibrates  5000  times  in  the  fpace  of  a 
fecond.  Neither  does  the  tafte  teach  us  that  the 
cryftals  of  fea  fait  are  of  a cubical  figure.  Laftly, 
motion  imparted  by  a body  perceived  by  the  fenfes, 
is  indeed  propagated  to  the  brain,  but  the  mind 
neither  perceives  this  motion,  nor  the  tremors  of 
found,  nor  the  percuffion  of  the  rays  of  light,  but 
fomething  perfeftiy  diftindl  from  motion.  It  is 
ehablilhed  as  a reciprocal  law  by  the  Creator,  that 
with  certain  changes,  produced  firh  in  the  nerve, 
and  then  in  the  fenforium  commune,  new'  and  defi- 
nite thoughts  fhall  arife  in  the  mind,  invariably 
connected  ; and  that  cur  perceptions  of  external  ob- 
jefls  are  arbitrary,  yet  that  they  are  not  falfe,  ap- 
pears plainly  from  the  perpetual  agreement  of  fim- 
ilar  ideas  with  fimilar  affections  of  the  fentient 
nerves,  in  all  perions  at  the  fame  timCj  and  in  one 
perfon  at  different  times. 

DLVii.  Therefore,  when  w^e  feel,  fi\*e  very  differ- 
ent exiftences  are  conjoined  : the  thing  which  w'e 
p"vreiv'e  ; the  affc<Tlon  of  the  organ  of  fenfe  by  that 

body  ; 


Chap.  XVIL  INTERNAL  SENSES.  271 

body ; the  afFeftion  of  the  brain,  arihng  from  the 
percuffion  of  that  fenfory  ; the  change  produced  in 
the  mind  j and,  laftly,  the  confcioufnefs  of  the 
mind,  and  perception  of  the  fenfation. 

DLvni.  It  appears  from  certain  experiments,  that 
the  firft  origin  of  every  fentient  nerve  is  always  dif- 
tinft  from  all  the  others  j and  that  the  change 
which  is  firft  excited  by  external  objedls  in  that 
nerve  (dlvi.)  continues  long  in  its  origin  ; and 
that  thofe  changes  are  generally  fo  arranged  in  the 
faid  part  of  the  brain,  that,  being  difpofed  accord- 
ing to  the  order  of  time,  thofe  are  neareft  together, 
which  were  either  c.otemporary,  or  occurred  in  im- 
mediate fucceflion  ; or,  laftly,  thofe  which  have  a 
relation  to  the  famefubjeft,  or  were  excited  by  fim- 
ilar  objefts  j infomuch,  that  it  is  certain,  that  new 
ideas  are  conveyed  to  the  fame  part  of  the  brain 
where  others  of  the  like  kind  are  referved:  for 
otherwife,  neither  would  the  arbitrary  figns  of 
words  and  letters  recall  to  the  memory  paft  ideas ; 
or  difagreeable  ideas,  returning  into  the  mind,  with- 
out the  aftiftance  of  external  objefls,  reproduce  the 
fame  effedls,  as  objefts  themfelves  ; nor,  otherwife, 
could  there  be  fo  conftant  and  manifeft  a connection 
of  analogous  ideas,  which  fupervene  moft  remark- 
ably in  dreaming,  to  the  corporeal  impreffions,  a<ft- 
ing  at  that  time  moft  powerfully.  Imagination 
and  memory  depend  on  this  confervation  of  ideas. 
Thofe  changes  conferved  in  the  fenforium,  which 
many  term  ideas,  are,  for  the  fake  of  diftinClion,  by 
us  called  the  impreffions  of  things,  as  they  do  not  ex- 
ift  in  the  mind,  but  are  imprefled  in  the  body  itfelf, 
and  indeed  in  the  medulla  of  the  brain,  in  an  in- 
comprehenfible  manner,  by  certain  characters,  in- 
credible in  their  minutenefs,  and  infinite  in  their 
number.  Amongft  thefe  the  impreffions  received 
by  the  fight  are  the  moft  remarkable,  and  moft  dif- 
tinCtly  preferved,  and  next,  thofe  of  hearing  j thofe 
of  the  other  organs  are  more  confufed,  and  lefs  re- 
vocable 


INTERNAL  SENSES.  Chap.  X\TI. 


£72 

vocable  by  the  will.  Both  the  imprefllons  and  their 
figns  are  preferved ; the  latter  more  eafily ; the 
former,  however,  fo  far,  that  a painter  can  exprefs 
with  his  pencil  upon  canvas,  a face  fimiiar  to  the 
image  of  a familiar  face,  imprehed  upon  his  mind. 

DUX.  We  are  faid  to  imagine,  when,  by  means  of 
any  image  preferved  in  the  fenforial  part  of  the  brain, 
the  fame  ideas  are  excited  in  the  mind  which  would 
arife  if  the  fentient  nerve  that  firft  produced  the 
faid  image  itfelf  fuffered  that  change.  This  we  term 
recalling  an  image.  This  definition  is  confirmed 
by  the  example  of  the  great  ftrength  of  fancy  in 
certain  perfons,  and  in  thofe  who  are  delirious,  and 
in  every  perfon,  in  the  inftance  of  dreams,  in  which 
thoughts  arife  in  the  mind,  occafioned  by  the  images 
preferved  in  the  brain,  not  at  all  weaker  than  thofe 
which  are  primarily  produced  by  the  change  in  the 
fentient  nerve,  from  the  external  objects,  and  in 
which  the  perfect  refemblances  of  perfons  and  things 
v/ith  which  we  are  occupied,  are  reprefented  to 
the  mind.  Attention^  quiet,  and  the  abfence  of 
other  objects,  even  obtain  a ftronger  affent  of  the 
mind  to  thefe  traces  imprefl’ed  on  the  brain,  than 
to  thofe  perceptions  which  are  excited  in  the  m.ind 
by  external  objects  : for  the  will  is  much  more 
powerfully  determined  in  thofe  who  dream,  than 
in  thofe  who  are  awake  ; and  fome  voluntary  muf- 
cles  perform,  during  lleep,  funftions,  which,  while 
awake,  they  never  could  perform,  even  when  their 
nerves  were  moft  ilrongly  affected  by  the  fame  ob* 
jeft.  From  hence  we  may  underftand,  how  it  is 
pofiible,  that  a very  vivid  internal  impreiiion  in  de- 
lirium, may  fo  impofe  upon  the  mind,  as  to  be 
roiftaken  for  the  perception  of  an  external  objedl  j 
which  is  evident  in  the  fparks  which  are  excited  by 
rubbing  the  optic  nerve  ; in  the  rednefs  feen  by 
the  eye  when  Ihut ; in  the  vertigo  that  arifes  from 
a miotion  of  the  retina,  which  we  afcribe  to  the  ex- 
ternal objects  themfelves  j in  double  vifion,  &c. 

DLX. 


Chap.  XVII.  INTERNAL  SENSES.  275 

DLX.  Memory  is  faid  to  be  exerclfed,  when  any 
thought  of  the  mind,  or  image  of  an  external  ob- 
jed:  preferred  in  the  fentient  part  of  the  brain, 
(cccLXXii.)  excites  any  perception  in  the  mind. 
This  is  commonly  weaker  than  in  imagination,  and 
almoft  confined  to  certain  arbitrary  figns,  which 
the  mind  conjoined  with  that  idea  at  its  firfi:  per- 
ception. For  memory  hardly  reprefents  the  images 
and  pidlures  of  things  to  the  mind,  but  almoft  only 
words,  and  certain  attributes,  and  abftrad  ideas  ; 
for  which  reafon,  it  excites  volition  lefs  pow'erful- 
ly.  But  it  appears  from  the  obfervation  of  the  phe- 
nomena of  memory,  that  thofe  changes  which  arife 
from  the  external  ienfes,  remain  long  in  the  brain  ; 
and  fometimes,  if  they  made  a ftrong  imprelfionj 
are  reprefented  to  the  mind  for  a long  period,  al- 
moft forever  ; but  that  they  are  gradually  weaken- 
ed and  impaired  ; unlefs  they  be  renewed,  either  by 
the  objed  being  reprefented  again  to  the  mind,  or 
by  the  mind  itfelf  recalling  the  fame  change  again 
into  memory  ; and  that  at  laft  the  change  will  be 
in  a manner  erafe'd,  and  entirely  loft,  and  the  idea 
which  was  conneded  with  that  change  by  the  law 
of  nature,  will  never  again  recur  to  the  mind.  This 
annihilation  is  gradually  effeded  by  new  and  dif- 
ferent impreffions  made  on  the  fenforium,  and  not 
from  time  only,  or  the  circulation  of  the  blood,  as 
in  cataleptic  patients,  who  fometimes,  after  a con- 
fiderable  interval  of  time,  return  to  the  fame  train 
of  thought  which  the  difeafe  had  interrupted.  But 
fometimes  all  of  them  will  be  fuddenly  deftroyed 
by  fome  difeafe,  in  which  the  brain  is  in  fome  way 
com.prefled,  either  by  the  blood  or  any  other  caufe. 
Such  a caufe,  ading  on  part  of  the  common  fenfory, 
blots  out  a part  of  the  impreffions  from  the  memo- 
ry, fuch  as  certain  words,  or  all  of  them,  the  cha- 
raders  by  which  we  exprefs  words,  or  our  friends, 
and  even  the  necelfaries  of  life : yet  all  thefe  im- 
preffions may  often  be  rene’wed  by  removing  the 
T compreffing 


INTERNAL  SENSES.  Chap.  XVII. 


274 

compreiling  caufe.  But  the  ftrength  and  duration 
of  an  idea  depend  upon  its  being  unuiual,  exceffive, 
or  greatly  conducing  either  to  increafe  or  leffen  our 
felicity  ; and,  lafdy,  upon  our  attention  to  it,  and 
repetition  ; which  laft  renders  the  impreflions  fo 
vivid,  that  their  perception  is  at  length  miftaken  by 
the  mind  for  the  perception  of  external  objects,  as 
in  the  cafe  of  maniacs. 

DLxi.  Moreover,  if  we  review  the  hiftory'  of  hu- 
man life,  it  appears,  that  in  early  infancy,  we  have 
hardly  any  memory  ; only  fimple  perceptions,  that 
foon  vanilh  : which,  nevertheless,  excite  ftrong  ideas 
in  the  mind,  as  we  fee  from  the  crying  of  infants. 
The  memory  is  perfected  by  degrees  ; and  the  ideas 
received  from  favorite  objects,  and  familiar  perfons, 
remain  imprelTed  in  the  mind  of  the  infant ; while, 
at  the  fame  time,  the  imagination  likewife  increafes, 
which  is  often  very  powerful  in  young  children  ; 
as,  for  example,  in  terror,  which  in  no  age  produces 
more  violent  or  deplorable  effects.  Afterwards,  as 
the  number  of  our  ideas  increafes,  the  facility  of 
preferving  paft  ideas  is  impaired,  and,  at  the  fame 
time,  the  power  of  the  imagination  becomes  torpid  : 
till  at  laft  the  former  almoit  perifhes,  and  the  ideas 
whicii  are  received  efcape  from  the  brain  in  a fhort 
time ; while,  at  the  fame  time,  the  imagination, 
which  is  a kind  of  memory,  languiflres. 

DLxii.  But  lince  thefe  perceptions  produce  vari- 
ous changes  in  the  mind  itfelf,  which  are  perfectly 
diftiilff  from  any  corporeal  faculty,  we  fliall  briefly 
add  fom.ething  concerning  them,  fo  far  as  may  fuf- 
fice  for  the  purpofes  of  medicine.  Thought  re- 
fides  in  the  foul,  it  attends  to  the  fenfations  which 
are  either  brought  by  the  fenfes,  or  recalled  by  the- 
imagination  ; frequently  alfo  to  the  mere  figns 
which  recur  into  the  mind.  Attention  is  when  one 
idea  occupies  the  mind  principally  or  folely  for  any 
length  of  time.  The  coraparifon  of  two  ideas,  in- 
fdtuted  by  the  mind,  is  called  judgment  or  genius, 

when 


Chap.  XVIL  INTERNAL  SENSES.  275 

icvhen  the  mind,  by  comparing  them,  difcovers  them 
to  be  alike  or  diffimilar.  Genius  confifts  in  a vivid 
fenfation  conjoined  with  rapidity  of  thought,  fo  as 
inftantly  to  abftraft  from  notions  their  points  of 
fimilitude  and  diffimilitude.  The  principal  fource 
of  judgment,  invention,  and  wifdom,  conhfts  in  the 
flow  examination  of  ideas,  by  which  they  are  con- 
fldered  by  the  mind  in  every  point  of  view,  and  in 
the  attention  of  the  mind  being  confined  to  one  ob- 
ject, to  the  exclufion  of  all  other  ideas.  Kence  the 
efficacy  of  darknefs  in  making  difficult  calculations ; 
the  exquifite  attention  of  blind  people  to  the  na- 
ture of  founds  j and  of  thofe  who  are  deaf,  to  col- 
burs.  The  fources  of  error,  are  negligence  in  con= 
templating  the  whole  idea,  the  eftimating  it  from  a 
partial  view,  and  the  connection  of  ideas  vrith  oth- 
ers that  are  diftihCt,  and  only  related  by  accident, 
or  external  caufes; 

DLXiii;  The  integrity  of  the  judgment  depends 
upon  a healthy  conftitution  of  the  brain-  For  when 
that  is  comprefled,  irritated,  exhaufted  of  blood,  or 
changed  in  its  fabric,  the  ufe  of  reafon  is  totally 
difturbed ; the  ftrong  internal  impreffions  on  the 
brain  are  reprefented  to  the  mind  as  external  or 
real  objeCts  ; the  chain  of  ideas  is  broken,  fo  that 
the  mind  does  not.  compare  them,  or  perceive  their 
refemblance  or  diverfity,  but  pafles  abruptly  from 
one  idea  to  another  totally  different ; or,  laftly,  the 
actions  of  the  feiifes  being  impaired  or  interrupted, 
and  all  impreffions  being  in  a manner  erafed  from 
the  brain,  man  is  reduced  to  a ftate  of  imbe- 
cility or  vegetation.  But  external  caufes  alfo 
have  confiderable  influence  in  changing  the  rela- 
tion of  the  mind  to  the  impreffions  of  the  fenfes  ; 
the  air.  Way  of  life,  food,  and  habit,  either  affift 
or  diminifli  the  foundnefs  of  the  judgment,  the 
force  of  the  imagination,  and  the  ftrcngth  of  the 
memory. 

T 2 


DLXIV.. 


mXERNAL  SENSES.  Chap.  TYlt 


276 

DLXiv.  Finally,  as  thefe  ideas  are  either  indifTer- 
ent,  or  have  foine  relation  to  our  happinefs,  they 
produce  different  determinations  in  the  will.  Some 
of  the  caufes  by  which  the  felicity  of  our  mind  is 
either  incrcafed  or  diminiffied,  proceed  entirely 
from  the  body,  and  are  purely  mechanical ; amongll 
thefe  are  pain,  difagreeable  fenfations,  \\hich  feem 
to  be  produced  by  every  fenfation  in  a nerve  that 
is  too  ftrong,  and  pleafure,  in  which  the  nerve  is 
irritated  beyond  what  is  ufual,  but  in  a moderate 
degree;  Itching  is  akin  to  pleafure,  and  in  both 
the  flow  of  blood  is  increafed  into  the  part  in 
v\'hich  either  pleafure  or  titillation  is  perceived  ; 
but,  when  farther  increafed,  it  degenerates  into 
pain,  or  exceflive  fenfation  in  the  nerve.  Anxiety 
is  from  the  blood  being  retarded  in  its  paffage 
through  the  lungs.  Other  ideas  which  affect  the 
mind,  are  either  entirely  unconnected  with  the 
properties  of  m.atter,  or  certainly  lefs  Ample,  under- 
Itood,  or  mechanical,  than  the  foregoing.  The  pre- 
fence of  good  conftitutes  joy  ; the  deAre  of  good, 
love  ; the  expeftation  of  good,  hope  : the  prefence 
of  evil,  forrow,  terror,  or  defpair  ; the  diflike  of 
evil,  hatred  ; and  the  expeftation  of  evil,  fear. 
Hope,  curioAty,  and  glory,  feem  to  be  affections  of 
the  human  mind,  which  neither  belong  to  the  bo- 
dy, nor  exift  in  beafts. 

DLXV.  From  thefe  affections  of  the  mind,  not 
only  the  pure  will  appears  to  direct  the  actions  of 
the  body  to  a forefeen  purpofe,  in  order  to  attain 
good,  and  avoid  evil,  but  allb  in  the  body  itfelf, 
neitiier  willing  tliem  nor  capable  of  oppoAng  them, 
various  changes  happen  in  the  pulfe,  refpiration, 
appetite,  ftrength,  and  other  functions  of  the  heart, 
nerves,  ftomach,  and  other  parts,  which  both  im- 
medi.ttelv  follow  and  indicate  the  paflions  of  the 
mind.  Thus  anger  violently  excites  the  m.otion 
of  the  fpirits,  increafes  the  motion  of  the  heart, 
the  frequency  of  the  pulfe,  and  the  ftrength  of  the 

mufcles  j 


Chap.  XVII.  INTERNAL  SENSES. 


277 

mufcles  ; forces  the  blood  into  the  ultimate  and 
pellucid  veffels,  and  even  out  of  the  vefTels  ; accele- 
rates the  excretion  of  bile,  terminates  chronic  dif- 
eafes,  and  removes  obftruclions.  Grief  weakens 
the  ftrength  of  the  nerves,  and  action  of  the  heart ; 
retards  the  pulfe  ; deftroys  the  appetite  ; and  pro^ 
duces  palenefs,  cachexy,  diarrhoea,  jaundice,  fcir- 
rholities,  and  difeafes  ariling  from  a ftagnation  of 
the  humours.  Fear  diminiflres  the  force  of  the 
heart,  fo  as  to  occafion  polypufes,  and  palenefs 
weakens  the  mufcular  motions,  relaxes  the  fphinc- 
ters,  increafes  inhalation,  and  diminillies  exhala- 
tion. Exceffive  terror  increafes  the  ftrength  even 
to  convulfion  ; excites  the  pulfe  ; removes  obftruc- 
tions,  palftes  ; interrupts  the  courfe  of  the  blood, 
and  produces  fudden  death.  Love,  hope,  and  joy, 
promote  perfpiration,  quicken  the  pulfe,  promote 
the  circulation,  increafe  the  appetite,  and  facilitate 
the  cure  of  difeafes.  Exceffive  and  fudden  joy  often 
kills,  by  increafing  the  miotion  of  the  blood,  and 
exciting  a true  apoplexy.  Shame,  in  a peculiar 
manner,  retains  the  blood  in  the  face,  as  if  the 
veins  were  tied  ; and  alfo  fuppreftes  the  menfes, 
and  has  been  even  known  to  kill. 

DLXVi.  In  what  manner  are  thefe  changes  pro.- 
duced  by  the  refpecfive  paffions  of  the  mind  ? Do 
nervous  fphinflers  regulate  the  veflels,  and  at  one 
time  comprefs  them  fubfultorily,  and  increafe  the 
motion  of  the  blood,  and  at  another  relax  them 
and  deftroy  their  tone  ? That  fomething  like  this 
obtains  in  the  fmaller  veflels,  appears  evidently 
from  the  very  fimilar  effefts  produced  by  fear  and 
cold  upon  the  nerves  of  the  Ikin,  In  the  genital 
parts,  we  manifeftly  fee  the  veins,  under  particular 
circumftances,  conftricled,  and  a confequent  accu^ 
mulation  of  blood : and  it  feemed  probable,  that 
in  the  larger  veflels,  the  nervous  noofes  furrounding 
tnany  of  them  produced  the  fame  eflecls  ; for,  in 


INTERNAL  SENSES.  Chap.  XVII. 


278 

various  parts,  they  furround  and  include  the  me- 
ningeal, temporal,  vertebral,  carrotid,  fubclavian, 
cceliac,  mefenteric,  renal,  and  other  arteries.  But 
after  it  was  fliewn  by  our  experiments,  that  the 
nerves  are  at  reft  during  the  action  of  the  mufcles, 
and  cannot  be  rendered  Ihorter  by  any  irritation, 
we  were  obliged  to  defert  this  elegant  theory.  Nor 
would  it  feem  far  from  the  truth,  that  the  arteries 
are  rendered  more  or  lefs  irritable  from  the  various 
fenfibility  of  the  nerves,  and  thus  may  be  con- 
traded  more  vehemently  or  languidly  by  the  fame 
quantity  of  blood,  and  that  thus  the  motion  of  the 
blood  is  either  quickened  or  retarded,  if  it  were  at 
all  certain  that  the  fmaller  arteries  have  the  fame 
irritable  nature  with  the  large  ones.  Thus  the  ap- 
petite and  periftaltic  m.otion  of  the  ftomach  and 
inteftines,  are  manifcftly  deftroyed  by  the  affections 
of  the  mind. 

DLxvii.  It  cannot  be  denied  that  the  Creator 
has  affixed  charaderiftic  marks  to  the  paffiions  of 
the  mind,  that  in  focial  life  man  might  not  eafily 
impofe  on  man.  For  the  refpedive  mufcles,  more 
efpecially  of  the  voice,  face,  and  eyes,  exprefs  the 
feveral  paffions  of  the  mind  fo  faithfully,  that  they 
may  be  even  reprefented  in  painting.  To  invei- 
tigate  each  of  them,  would  indeed  be  an  elegant 
taffi,  but  too  long  for  this  compendium.  From 
the  adion  of  thefe  mufcles  being  often  repeated, 
phyftognomy  arifes,  fo  that  the  conftant  expreffion 
of  the  face  retains  fomethino;  of  the  adion  of  the 
prevailing  mufcles  ; and  fome  charader  of  frequent 
anger  often  remains  in  the  countenance,  after  the 
paffion  itfelf  is  gone  off. 

DLXviii.  Whence  proceeds  the  fympathy  of  parts, 
fo  fanaous  in  the  pradice  of  phyfic  ? In  fome  of 
them  it  appears  to  depend  upon  the  connedion  of 
the  blood-veftels ; by  which  tlie  blood,  being  repelled 
from  one  part,  prelTes  more  hea\  ily  upon  another, 
which  has  its  vtffds  from  the  fame  common  trunk, 

i'his 


Chap.  XVH.  INTERNAL  SENSES. 


279 


This  comprehends  reyulfions  made  by  blood  let- 
ting j headach,  from  cold  feet,  &c.  In  other  parts, 
the  fympathy  arifes  from  a fimilitude  in  their  fab- 
ric, by  which  they  fuffer  like  effects  from  the  fame 
caufes  ariiing  in  the  body,  fuch  as  the  fympathy 
betwixt  the  womb  and  the  bpeafts.  Another  caufe 
is,  the  continuity  of  membranes,  from  hence  the 
itching  in  the  glans  of  the  penis  from  calculus,  the 
cure  of  deafnefs  by  diarrhoea.  Another  caufe  ex- 
ifts  in  the  nerves  themfelves,  and  their  anaftomofes, 
as  fatisfaclorily  appears  from  the  teeth  being  fet  on 
edge  by  certain  founds,  a diiagreeable  fenfation  be- 
ing produced  in  the  maxillary  nerve,  on  account 
of  its  various  communications  with  the  portio  du.- 
ra.  Thus  the  fympathy  of  the  eyes,  which  is  not 
obfervable  in  like  manner  in  the  ears,  proceeds 
from  the  decuffation  of  the  optic  nerves  5 and  vom- 
iting is  excited  by  nephritis.  Laftly,  another  caufe 
is  referred  to  the  common  fenfory,  and  beginnings 
of  the  nerves,  which  is  demcnftrated  from  generaj 
convulfions  being  produced  by  the  irritation  of  a 
fingle  nerve,  and  univerfal  epilepfy  by  a local  dife 
order,  &c.  Some  fympathies  in  difeafes  arife  from 
a tranllation  of  the  matter  to  other  parts  through 
the  cellular  fubftance,  or  by  the  aftion  of  the  mufe 
cles,  arteries,  or  gravity, 

DLxix.  But  that  important  fympathy  remains  to 
be  explained,  which  fubfifts  betwixt  the  body  and 
the  mind.  For  that  the  nature  of  the  mind  is  dif- 
ferent from  that  of  the  body,  is  proved  by  an  in.? 
finity  of  circumftances,  efpecially  by  ideas  and  afe 
feclions  of  the  mind,  to  which  nothing  in  fenfation 
is  analogous,  For  what  is  the  colour  of  pride?  or 
what  the  magnitude  of  envy  or  curioiity  ? to  which 
there  is  nothing  fimilar  in  animals  ; neither  can 
that  good  which  is  delired  by  it,  glory  and  the  acr 
quihtion  as  it  were  of  new  ideas,  be  referred  to  any 
corporeal  pleafure.  Is  it  poffible  that  the  body 
can  poffefs  two  kinds  of  forces,  fo  that  its  infinite 

particles 


INTERNAL  SENSES.  Chap.  XVII. 


2§o 

particles  fliould  unite  into  one  mafs,  which  do  net 
preferye  their  own  affections  only,  and  reprefent 
them  to  themfelves,  but  alfo  join  together  into  one 
common  thinking  whole,  differing  from  the  attri- 
butes of  all,  and  yet  capable  both  of  receiving  and 
comparing  thefe  attributes  ? Is  there  any  inftance 
of  a body,  which,  without  an  external  caufe,  paffes 
from  reft  to  motion,  changes  or  reverfes  the  direc- 
tion of  motion,  without  the  action  of  feme  other 
caufe,  as  is  very  eafily  obferved  with  regard  to  the 
mind  ? 

DLXX.  Yet  this  m.ind,  fo  different  from  the  body, 
is  connected  with  it  by  the  molt  intimate  ties,  be- 
ing both  obliged  to  think  upon  thofe  impreffions 
which  the  body  prefents  to  it,  and  not  feeming  to 
poffefs  memory  or  judgment,  independent  of  the 
corporeal  imprellions  on  the  brain  ; and,  laftly,  by 
means  of  volition  being  the  caufe  or  occafion  of  the 
greateft  and  fwiteft  motions  of  the  body. 

DLXxi.  Thofe  have  acted  circumfpeedy  vko,  con- 
feffmg  themfelves  ignorant  of  the  manner  in  which 
the  body  and  mind  are  united,  have  contented 
themfelves  with  the  laws  effablilhed  by  the  Creator, 
which  they  have  afeertained,  and  not  conjectured. 
They  are  manifeftiy  excufed  by  the  obfervation, 
(onvn)  that  even  in  optics,  it  is  very  certain  that 
the  affections  of  the  body  are  connected  with  the 
thoughts  of  the  mind,  by  an  arbitrary  relation,  and 
that  other  ideas  evould  have  been  fuu'Sfefted,  if  the 
Creator  had  altered  the  figure,  the  refracting  pow- 
er, or  colours  of  the  parts  of  the  eye.  As  there  is 
a law,  which  effabliffres  a perpetual  connection  be- 
tween the  leak  refrangible  rays  and  the  idea  of  a 
red  colour  ; there  is  alio  a law  which  conftitutes 
the  conneciion  betwixt  the  iixxpreflicn  of  thofe  rays 
upon  the  retina,  and  the  cerrefponding  idea.  Nor 
need  we  be  more  afham.ed  of  our  ignorance  of  the 
mechanifm.  of  the  latter  law,  than  of  cur  ignorance 
of  the  nature  of  the  former. 


ELrerni. 


Chap.  XVII.  INTERNAL  SENSES. 


281 


DLXxii.  Does  the  mind  govern  the  body  ? Do 
all  the  motions  and  adions  in  the  body  arife  from 
the  mind,  as  the  immediate  fource  and  origin  of 
motion  ? Do  the  motions  of  the  heart,  arteries,  and 
refpiration,  arife  from  the  mind,  willing  them  and 
folicitous  for  the  common  good  of  the  whole  fyf- 
tem  ? Is  this  power  of  the  mind  demonhrated  by 
the  ftrudure  of  polypi  form.ed  in  wounds,  by  the 
paffions  of  the  mind,  and  by  the  nsevi  materni  ? Is 
the  abfenee  of  confdpufnefs  accounted  for  by  the 
well  known  example  of  the  obfcure  perceptions 
we  have  in  refpiration,  winking,  and  mufcular  mo- 
tion, all  of  which  are  effeded  by  the  will,  although 
we  do  not  know  the  organs,  or  attend,  that  we 
will,  when  we  breathe,  wink,  or  walk,  when  occur 
pied  in  thought  ? Is  it  therefore  certain,  that  all 
motions  arife  from  the  mind,  becaufe  there  is  no 
other  evident  caufe  perpetually  conneded  with  the 
body,  to  which  they  can  be  referred  ? 

DuxxHi.  There  are  many  reafons  which  do  not 
yet  permit  us  to  adopt  this  opinion.  And,  lirft,  the 
conilrudion  and  government  of  the  body  itfelf  ap- 
pear greatly  to  exceed  the  wifdom  of  the  mind. 
Our  mind  fees  one  point  diftindly,  (dlv.)  and 
thinks  one  thought  diftindly  ; but  if  it  endeavours 
to  fee  two  objects  at  the  fame  time,  to  contemplate 
two  ideas  at  the  fame  timely  or  to  read  two  letters  at 
once,  it  always  becomes  confufed,  commits  mif. 
takes,  and  comprehends  neither  rightly  ; and  con- 
fcious  of  its  own  powers,  whenever  it  applies  feriouf- 
ly  and  diligently  to  any  objed,  it  withdraws  itfelf 
as  it  were  from  the  impreflions  of  fenfe,  and  nei- 
ther fees,  nor  hears,  nor  fmells,  nor  performs  muf- 
cular  adions.  But  the  mind  ought  to  be  capable 
of  infinite  and  diftind  thoughts,  in  order  to  be  able 
to  govern  fuch  an  infinite  variety  of  mufcles,  veft 
fels,  and  fibres,  in  a manner  accommodated  to  the 
moft  exad  geometry ; and  to  refolve  and  conftrud 
pccafional  problems  in  the  diredion  of  the  muf- 
cles, 


2^2 


INTERNAL  SENSES.  Chap.  XVIf, 


cles,  fcarcely  foluble  by  the  higheft  geometry  ; and 
yet  we  muft  conclude  the  mind  ignorant  of  this  im- 
menfe  talk,  and  at  the  fame  time,  over  and  above 
all  thofe  works,  capable  of  contemplating  the  moft 
difficult  and  abftracf  ideas ; fo  that  neither  the  care 
of  the  body  difturbs  its  meditations,  nor  its  medita- 
tions interfere  with  the  necefl'ary  motions  of  the 
body. 

DLxxiv.  Moreover,  if,  without  being  confcious 
of  volition,  we  can  will  to  refpire,  or  vdnk,  and 
with  effecl : we  neverthelefs  retain  our  control, 
and  can  fufpend  refpiration,  and  keep  the  eyelids 
firm,  and  alternately  excite  their  actions,  and  there- 
fore we  never  lofe  either  the  confcioufnefs  of  our 
control,  or  the  ufe  of  it,  But  we  are  not  able  to 
perform  any  thing  of  this  kind  in  the  heart  or  in- 
teftines  ; we  cannot  reftrain  their  motion,  when  too 
quick,  or  excite  them  when  languid.  Amongfi.  ail 
mankind,  why  does  eveiy  one  govern  his  refpira- 
ton  ? why  in  all  ages  no  one  his  heart  ? If  cuftom 
only  is  the  caufe  of  our  inconfcioufnefs  of  this  pov'- 
er,  wffiy  is  not  the  mind  fenfible  of  its  action,  in 
moving  the  heart,  or  in  exercifing  the  periftaltic 
motion,  after  being  fufpended  for  hours,  or  even 
whole  days,  in  fwoons,  in  hyfteric  fits,  and  in  af- 
phyxia  ? 

DLXxv.  But  it  is  evidently  falfe,  that  all  mo- 
tions arife  from  the  mind,  and  that  without  it 
matter  would  be  an  immoveable  inert  mafs : for 
the  contractility  excitable  by  every  ftimulus,  to 
which  the  motion  of  the  heart,  inteftines,  and  per- 
haps all  the  other  motions  in  the  human  body,  be- 
long, (ccccxci.)  does  not  require  the  prefence  of 
the  mind  ; it  continues  in  the  dead  body  ; it  is  ex- 
cited by  mechanical  caufes,  heat,  and  inflation  ; 
and  it  does  not  defert  the  fibres,  until  they  become 
ftiff  and  cold,  although  the  mind,  which  perceives 
and  w’ills,  may  have  been  a long  time  expelled  by 
the  deftruCtion  of  the  brain  and  heart,  and  even 

althougli 


Chap.  XVII.  INTERNAL  SENSES.  283 

although  the  mufcle,  by  being  taken  out  of  the  bo- 
dy, has  been  feparated  from  every  imaginable  con- 
nexion with  the  mind. 

DLXxvi.  Little,  if  any,  reliance  is  to  be  put  in 
the  nsevi  materni,  as  is  noticed  in  another  place. 
That  the  direXion  of  the  vital  motions,  in  difeafes, 
is  not  regulated  by  prudence,  but  almott  entirely 
by  the  power  of  ftimulus  ; we  are  explicitly  taught 
by  the  moft  ancient  and  only  certain  pf  aXice,  which 
reftrains  the  exceilive  motions  in  acute  and  inter- 
mitting febrile  difeafes,  by  the  ufe  of  blood  letting, 
opium,  nitre,  Peruvian  bark,  &c.  The  fage  has 
no  prerogative  in  the  government  of  his  body,  over 
the  mereft  ideot ; and  that  the  foetus,  which  even 
at  birth  is  ignorant  of  the  motions  of  its  mufcles, 
and  learns  by  experience  to  walk,  to  fwallow  and 
to  fee,  conftruXs  its  body,  fabricated  with  fuch  in- 
credible art,  is  an  affirmation  fo  repugnant  to  prob- 
ability, and  fo  abfard,  that  of  itffiif  alone  it  is  faf- 
bcient  to  refute  the  hypothelis. 

DLxxvii.  The  ftate  of  aptitude  for  exercifing  the 
fenfes  and  voluntary  motion,  in  healthy  organs,  is 
called  wakefulnefs.  Indifpofition  to  fuch  exercife, 
and  their  perfeX  reft,  with  healthy  organs,  is  called 
deep. 

DLXxviii.  In  deep,  the  mind  either  thinks  not  at 
all  of  what  fhe  knows  or  retains  in  memory  ; or 
only  attends  to  the  traces  of  paft  objeXs  repofited 
in  the  common  fenfory,  (dlviii.)  the  vivid  repre- 
fentations  of  which  excite  altogether  the  fame  per- 
ceptions in  the  mind  as  are  made  by  the  impreffion 
of  external  objeXs  upon  the  organs  of  fenfe.  Thefe 
reprefentations  are  called  dreams  ; and  have  the  ef- 
feX,  that  while  the  reft  of  the  emporium  of  the 
fenfes  and  mufcular  motion  is  at  reft,  fome  part 
remains  open,  is  pervaded  by  the  fpirits  and 
watches.  Sometimes  certain  voluntary  motions  are 
conjoined  with  thefe  perceptions  of  the  mind,  fo 
that  the  organs  of  fpeech,  many,  or  all  of  the 

limbs, 


i86 


mXERNAL  SENSES.  Chap.  XML 

ways  from  the  motion  of  the  fpirits  through  the 
brain  being  impeded. 

DLxxxvi.  This  theory  is  confirmed  by  the  caufes 
of  vigilance  : for  all  thofe  things  prevent  ileep 
which  produce  plenty  of  fpirits  ; more  efpecially 
warm  aromatic  drinks,  which  fend  minute  Simula- 
ting particles  to  the  head ; by  which  the  motion 
of  the  blood  is  moderately  quickened  through  the 
brain,  and,  being  at  the  fame  time  more  diluted^ 
it  fecretes  more  fpirits  in  a given  time. 

DLXxxvii.  Sleep,  again,  is  prevented  by  cares  of 
the  mind,  attentive  and  interefting  meditation,  and 
pain  of  body  and  mind ; all  of  which  prevent  the 
fpirits  in  the  fenforium  commune  from  refting,  and 
the  nerves  from  collapfing.  Therefore,  the  rormer 
caufes  increafe  the  quantity  of  the  fpirits,  thefe  in- 
creafe  their  motion.  And,  therefore,  we  return  to 
our  former  conclufion  (dlxxxv.)  namely,  that  the 
nature  of  fleep  confifts  in  the  collapfe  of  the  nerves,- 
proceeding  from  the  fenforium  commune. 

DLXxxviii.  Is  the  region  of  lleep,  therefore,  in 
the  ventricles  of  the  brain  ? It  is  inconfiftent  with 
the  univerfality  of  lleep,  which  extends  to  animals 
which  have  no  ventricles  in  their  brain.  Do  the 
vital  aftions  continue  during  Seep,  becaufe  it  is  an 
affection  peculiar  to  the  brain,  and  independent  of 
the  cerebellum  ? And  what  is  the  caufe  of  this  di- 
Verfity,  which  occafions  the  animal  functions  to  reft 
during  lleep,  and  the  %dtal  functions  to  continue  ? 
it  is  that  already  mentioned,  that  vital  motions  are 
prevented  from  refting  by  perpetual  ftimuli,  and 
perpetually  exciting  caufes,  (cccxcii.) 

DLXxxix.  The  effe<Tt  of  lleep  is  the  abatement  of 
all  the  motions  in  the  human  body.  For  now  the 
action  of  the  heart  alone  remains  to  propel  aU  the' 
humours,  while  rdl  the  motions  of  tlie  mufcles  and 
fentient  nerves,  and  thofe  originating  from  the  pal- 
lions  of  the  mind  and  volition,  are  removed  ; by 
which,  while  awake,  the  courfc  of  the  blood  and 

fpirits 


Chap.  XVII.  INTERNAL  SENSES.  2S7 


fpirits  was  promoted,  as  well  as  by  the  heart  (dlxv* 
ccccxvii.)  The  heart  gradually  returns  from  its 
quick  and  almoft  feverifli  pulfation,  to  its  morning 
flownefs ; the  breathing  becomes  lels  and  flower, 
the  pcrillaltic  motion  of  the  ftomach  and  inteftines, 
hunger,  digeftion,  and  the  progreflion  of  the  feces, 
are  aU  diminiflied ; the  thinner  juices  move  more 
flowly,  while  the  more  fluggifli  are  coUecf  ed  togeth- 
er, and  the  effuied  fat  is  accumulated  ; the  nour- 
ifliing  jelly  adheres  more  plentifully  to  its  fibres 
and  cavities ; the  confum.ption  of  the  fpirits,  the  at- 
trition of  the  blood,  and  the  quantity  of  perfpira- 
tion,  are  all  diminiflied.  Thus,  while  the  nervous 
fluid  continues  to  be  fecreted,  and  its  confumption 
to  be  diminiflied,  it  is  by  degrees  accumulated  in 
the  brain,  fo  as  to  diflend  and  fill  the  collapfed 
nerves^  and  from  the  acceflion  of  the  flighteft  flim- 
ulus,  both  the  internal  and  external  fenfes  are  ex- 
cited to  aftion,  and  the  fyftem  is  awakened.  Sleep, 
continued  for  too  great  a length  of  time,  difpofes 
to  all  the  diforders  that  attend  flownefs  of  circula- 
tion, to  fatnefs,  drowflnefs,  and  cachexies  j and  is 
highly  detrimental  to  the  memory. 

Dxc.  Whence  the  yawning  of  thofe  about  to 
fleep  ? To  promote  the  paflage  of  the  blood  through 
the  lungs,  which  is  now'-  flower.  Whence  the 
ilretching  of  the  limbs  ? To  overbalance,  by  the 
influx  of  the  fpirits,  the  natural  contraction  of  the 
mufcles,  by  which  all  the  limbs  are  put  in  a mod- 
erate degree  of  flexion,  and  fo  to  reftore  ftrength  to 
the  extenfor  mufcles.  Whence  the  opinion,  that, 
during  fleep,  the  motion  of  the  heart  becomes  ftrong- 
er,  and  the  perfpiratron  more  plentiful  ? From  the 
heat  of  the  tedclothes,  by  which  the  perfpirable  mat- 
ter being  confined,  foftens  and  relaxes  the  Ikin.  But 
any  one  that  fleeps  in  his  ufual  garments,  grows  cold- 
er ; and  animals  which  fleep  through  the  winter,  be- 
come exceflively  cold,  as  dormice  and  hedge-hogs. 
Why  do  all  animals  grow  fleepy  after  taking  food  ? 


Not 


MASTICATION.  Chap.  X\Tli. 

Not  from  preffure  upon  the  aorta,  or  congeftion  of 
blood  in  the  brain ; for  even  animals  which  have 
fcarcely  any  brain,  Ileep  after  food.  Do  the  indigef- 
tible  particles  of  our  aliments,  by  palling  lefs  eafily 
through  the  brain,  and  comprefling  its  medulla,  ren- 
der the  fleep  lefs  refrefliing  ? Is  dreaming  perpetual 
and  infeparable  from  fleep  ? Is  it  fo  far  natural,  and 
a kind  of  fubftitute  for  fenfation  to  the  mind,  that 
it  may  never  be  without  thought  ? This  does  not 
feem  probable.  We  rather  aferibe  dreams  to  fome 
morbid  ftate,  or  to  fome  ftimulating  caufe,  inter- 
rupting the  perfect  reft  of  the  fenforium.  Hence 
that  fleep  refreflies  moft  which  is  without  dreams, 
or  at  leaft  wdthout  the  remembrance  of  them. 
Hence  they  are  generally  wanting  in  the  firft  fleep, 
at  which  time  the  fpirits  are  moft  exhaufted,  and 
return  in  the  morning  when  thefe  are  in  fome 
meafure  repaired.  Hence  care,  the  ftrong  impref- 
Con  of  fome  idea  upon  the  memory,  indigeftible 
food,  excefs,  or  any  uneafy  pofture  of  the  body,  oc- 
caflon  dreams  ; for  they  are  ufually  generated  by 
fome  fenfation,  vcith  which,  according  to  the  laws 
of  the  aflbeiation  of  ideas,  the  whole  coUedtion  of 
fimilar  impreflions  connect  themfelves. 


CHAP.  XVIII. 


OF  MASTICATION,  SALIVA,  AND  DEGLUTITION.' 


Dxci.  T_T ARD  and  tough  articles  of  food,  con* 
fifting  of  long  parallel  fibres,  or  cover- 
ed with  a bony  Ihell  or  cartilaginous  integuments, 
and  friable  fubftances,  generally  require  maftica- 
tion,  to  divide  them  into  fmaUer  and  lefs  coherin 
parts,  that  they  may  the  more  eafily  yield  to  th 
dilfolving  powers  of  the  ftomach.  The  more  com- 
pletely they  are  fubdivided  in  the  mouth,  they  be- 
come 


bn 


Chap.  XVIIL 


MASTICATION; 


2 


come  the  more  fapid,  approach  the  nearer  to  the 
nature  of  a fluid,  and  are  digefted  the  more  ea-' 
Jily. 

Dxcn.  Therefore  mofl:  animals  are  provided  with 
extremely  hard  teeth,  each  having  a bony,  hollow 
root  receiving,  through  a fmall  hole  in  the  apex  of 
its  cone,  little  blood-veflels,  and  a nerve,  which  go 
to  its  internal  periofteum  ; fixed  by  the  whole  root 
into  the  alveolus  adapted  to  it,  and,  in  the  upper 
part  of  its  crown,  ftrongly  tied  down  by  the  ad- 
hering gum.  But  the  upper  part  of  the  teeth  pla- 
ced above  the  gums,  is  not  bony,  but  of  a peculiar 
jflrufture,  much  harder  and  denfer,  refifting  putre- 
faftion  in  the  dead  body,  and  almofl;  vitreous,  com- 
pofed  of  flraight  fibres  vertical  towards  the  root, 
and  running  together  in  the  middle.  This  portion 
has  neither  periofteum  nor  veflels,  and  being  per- 
petually wafted,  feems  to  be  as  often  repaired  by 
fome  fluid  which  afcends  from  the  follicle  of  the 
root.  The  teeth  are  therefore  well  adapted  for 
overcoming  the  hardnefs  of  other  bodies,  and  for 
Comminuting  the  food. 

Dxciii.  As  the  materials  of  our  food  are  various 
in  their  texture  and  firmnefs,  nature  has  according- 
ly diverfified  the  ftrucfure  of  the  teeth.  In  man, 
the  anterior  teeth,  four  in  each  jaw,  are  weaker 
than  the  reft,  have  a Angle  root,  and  a crovrn  in- 
wardly concave,  outwardly  convex,  extenuated  like 
a wedge,  and  terminated  by  a reftilineal  edge.  They 
are  deftined  for  dividing,  into  fmaller  portions,  the 
fofter  foods,  which  are  merely  tough,  and  for  com- 
minuting the  fibres  and  membranes  of  animals  and 
vegetables,  and  the  kernels  of  fruits. 

Dxciv.  The  fecond  fpecies  is  the  canine  teeth, 
of  which  there  are  two  in  each  jaw,  fixed  by  a 
longer  and  ftronger,  but  Angle  roof,  with  a crown 
of  a conical  lhape.  Thefe  lacerate  tough  aliments, 
and  hold  faft  thofe  which  require  much  tritura- 
tion. 


IJ 


DXCV. 


290 


MASTICATION. 


Chap.  XVUh 


Dxcv.  The  third  order  is  the  grinders,  whicJ^ 
in  general  have  feveral  roots,  and  a quadrangular 
crown,  with  a fiat  furface,  but  divided  by  che- 
quered afperities.  The  two  anterior  ones  are  weak- 
er, have  one  or  two  roots,  with  the  furface  of  their 
crown  parted  into  two  ; the  three  pofterior  grind- 
ers are  larger,  fixed  by  three,  four,  and  fometimes 
five  roots,  but  generally  by  one  lefs  in  the  lower 
jaw,  with  a flat  furface,  quadrangular,  and  com- 
monly divided  into  as  many  eminences  as  there  are 
roots.  Betwixt  thefe  teeth,  the  bony  articles  of 
food  are  interpofed  and  broken,  the  hard  are  bruif- 
ed,  while  the  lower  teeth,  being  moved  obliquely 
and  laterally,  are  rubbed  againfl;  the  immoveable 
upper  ones : by  thefe  the  functions  of  the  teeth  arc 
principaiiy  performed. 

Dxcvi.  That  the  teeth  might  polfefs  mobility 
combined  with  ftrength  and  firmnefs,  the  upper 
ones  are  fixed  into  the  fockets  of  the  immoveable 
upper  jaw,  the  lower  ones  into  the  lower  moveable 
jaw,  which  is  a Angle  bone,  and  articulated  with 
the  temporals,  in  fuch  a manner  that  it  may  be 
drawn  down  from  the  upper  jaw,  and  raifed  up 
againfl  them  with  great  force  ; and  may  be  moved 
laterally  to  the  right  and  left,  and  forwards  be- 
yond the  upper  jaw,  and  backwards  to  its  firft  fitu- 
ation.  Thefe  motions  depend  upon  the  articula- 
tion of  its  condyles,  (in  which  the  lateral  parts  of 
the  loveer  jaw  terminate,  and  which  are  broadefl 
tranfverfely,  and  convex  in  the  middle,)  with  the 
oblique  tubercles  of  the  temporal  bones,  which 
are  hollowed  at  the  root  of  the  jugal  procefs,  deep- 
er in  the  middle,  and  increafed  by  a little  fi;it 
furface  of  the  fame  kind,  before  the  auditory  paf- 
fige,  from  which  it  is  feparated  by  a peculiar  fif- 
fure.  M'his  joint  has  greater  liberty  in  moving, 
and  a durable  cartilaginous  crufl,  from  a cartilage 
interpofed  between  the  condyle  of  the  lower  jaw 
and  the  tubercle  of  the  temporal  bone,  on  both  fides 

concave 


Chap.  XVIII.  MASTICATION.  ^gt 

toncave  in  its  middle,  with  raifed  edges,  corre= 
fponding  by  the  former  to  the  tubercle  of  the  tem- 
poral bone,  and  by  the  latter  to  the  adjacent  de- 
preffions. 

Dxcvn.  The  mufcies  moving  the  lower  jaW, 
which  in  man  are  weaker,  but  very  ftrong  in 
brutes,  are  the  temporalis,  an  elevator,  arifmg  from 
a large  part  of  the  fide  of  the  ikull,  and  from  its 
aponeurofis,  collecling  its  tendinous  fibres,  inter- 
mixed vith  mufcular  fibres,  in  a ftellated  manner, 
into  the  {harp  procefs  of  the  jaw ; the  malTetef,  an 
elevator,  defcending  double  or  triple  from  the  ju- 
gum  and  margin  of  the  cheek  bone  backwards  into 
the  coronoid  procefs.  Thefe  act  in  concert ; but 
the  temporal  mufcle  carries  the  jaw  more  back- 
wardsj  the  maffeter  more  forwards.  The  pterygoi- 
deus  internus  deicends  from  the  pterygoid  foITa, 
and  from  the  palate  bone  and  root  of  the  little 
pterygoid  procefs,  and  its  internal  wingj  into  the 
angle  of  the  lower  ja.w,  which  it  elevates  when  de- 
prefled  by  its  antagonifts,  or  draws  to  one  fide. 
The  pterygoideus  externus  has  a double  origin  ; 
the  one  tranfverfe  from  the  inner  wing  and  adja- 
cent bone  of  the  palate,  and  pofterior  convexity  of 
the  upper  jaw : the  other,  defcending,  arifes  from 
the  hollow  temporal  part  of  the  great  wing  of  the 
fphenoides ; thence  it  proceeds  backwards  and  down- 
■wards  into  the  outer  part  of  the  condyle  of  the  low- 
er jaw,  which  it  draws  forw^ards  before  the  upper 
jaw,  and  to  one  fide. 

Dxcviii.  The  lower  jaw  is  deprefled,  and  the 
mouth  opened  by  the  digaftric  m.ufcle,  arifing  from 
a hollow  of  the  mamillary  procefs,  tied  by  its  mid- 
dle tendon  wfith  much  firm  cellular  fubilance,  of  a 
tendinous  nature,  to  the  os  hyoides  ; likewife  con- 
neffed  to  the  mylohyoideus,  and  pafiing  through 
the  defcending  fibres  of  the  fiylohyoideus,  increaf- 
ed  by  another  flelhy  belly,  and  inferted  at  the  fym- 
phyfis  of  the  two  halves  of  the  lower  jaw.  More- 
u 2 over. 


MASTICATION. 


Chap.  XVIII. 


292 

over,  the  mouth  may  be  opened  by  all  the  other 
mufcles,  inferted  into  the  inferior  maxilla,  os  hy- 
oides  and  larynx,  as  the  gciiiohyoideus,  mylohyoi- 
detis,  geniogloITus,  Ilernohyoideus,  Ilernothyroide- 
las,  coracohyoideusy  and  latiffimus  colli ; although 
the  latter  rather  draws  the  ikin  of  the  neck  and 
face  downwards.  The  gcniohyoidcus  and  digaftric 
mufcles  draw  the  jaw  backwai'ds. 

Dxeix.  The  lower  jaw  is  elevated  with  great 
force,  and  the  lower  teeth  being  carried  up  againft 
tiie  upper  teeth,  divide  the  food,  by  the  aclion  of 
the  temporal,  maffeter,  and  internal  ptery  goid  muf- 
cles ; which  appears  by  undoubted  experiments  to 
be  very  powerful,  and  iuflicient  to  raife  fever al  hun- 
dred weight.  The  lateral  motions  of  the  jaw,  and 
its  circular  motion  around  one  condyle  as  a fixed 
point,  are  performed  by  the  external  and  internal^ 
ptcrygoidei,  and  by  the  former  mufcles  acting  fin- 
gly  and  alternately^  Thus  the  food  is  cut,  broken 
and  bruifed  ; and  if  the  mallication  be  rightly  per- 
formed, it  is  reduced  into  a kind  of  pulp. 

DC.  Before  the  teeth  there  is  placed  a cutaneous 
and  flellry  fack,  which  is  every  where  produced 
from  the  integuments  of  the  face  ; and  inclofes  a 
hollow  fpace  with  both  rows  of  teeth  when  fhut. 
The  lateral  parts  are  called  the  cheeks,  the  middle 
the  lips.  From  this  cavity  there  is  a paflage,  be- 
twixt the  teeth,  into  the  mouth,  which  on  the  up- 
per part  is  bounded  by  the  bony  and  foft  palate, 
underneath  by  the  mufcles  lying  under  the  tongue, 
and  on  the  forepart  by  the  teeth.  On  the  back 
part  it  opens  between  the  foft  palate  and  tongue 
into  the  fauces,  d'he  tongue  divides  the  cavity  of 
the  mouth  in  the  middle,  and  is  eafily  moveable  to- 
every  part  of  it. 

Dci.  During  the  trituration  of  the  food  in  the 
mouth,  there  is  continually  poured  to  it  a large 
quantity  (;f  a watery  clear  liquor,  cvaporablc,  inii- 

pid. 


CfiAP.  xviir. 


SALIVA. 


293 

pid,  or  very  little  faline,  containing  a very  fmall 
quantity  of  earth,  and  neither  acid  nor  alkaline,  al- 
though from  it  a very  fmall  portion  of  lixivial  fait 
may  be  obtained ; of  which  all  around  are  numer, 
ous  fources.  A large  quantity  of  this  faliva  is  fe- 
creted  by  innumerable  oval  glands  in  the  lips  and 
cheeks,  and  by  fome  larger  ones  which  are  placed 
round  the  mouth  of  the  parotid  du6l ; and  laftly, 
by  the  pores  of  the  hard  palate,  pouring  out  the 
liquor,  which  they  fecrete,  through  a little  fhort 
duel  and  hole.  The  fluid  efTufed  by  the  exhaling 
veffels  of  the  cheeks,  and  back  of  the  tongue,  is 
ftmilar,  or  more  watery.  It  is  now  afeertained,  that 
the  duclus  incifivus  is  impervious,  and  tranfmits 
nothing  but  the  artery,  w'hich  goes  from  the  palate 
to  the  noftrils. 

Dcii.  The  faliva  is  a watery  liquor,  with  a fmall 
quantity  of  fait,  partly  lixivial,  and  partly  culi- 
nary ; with  fome  oil  and  earth,  evaporable  by  the 
fire  ; with  fcarcely  any  tafte,  unlefs  when  fharpened 
by  difeafe  or  hunger.  The  quantity  produced  is 
confiderable,  as  twelve  ounces  have  been  known  to 
flow  out  from  wounds  in  the  fpace  of  an  hour.  By 
well  bred  people,  it  is  for  the  mofc  part  fwallowed; 
and  ufefully,  as  it  cannot  be  thrown  av/ay  without 
hurting^  the  dia;efl:ion. 

Dciii.  The  falivary  glands  efpecially  fupply  the 
faliva.  Of  thefe,  the  principal  is  the  parotid,  exten- 
flvely  filling  up  the  interval  between  the  auditory 
paflage  and  the  lower  jaw,  and  covering  the  jaw- 
bone where  naked,  and  part  of  the  mafieter.  It  is 
a conglomerate  gland,  with  round  acini,  connected 
by  cellular  fubllance  ; which  more  denfely  com- 
pacted, forms  a kind  of  involucrum,  almoft  tendi- 
nous, to  the  whole  gland.  Its  du<T  is  white,  vafeu- 
lar,  and  capacious,  afeending  from  the  bottom  of 
the  gland  to  the  jugum,  from  whence  it  is  tranf- 
verfely  inclined,  and  receives  the  du6l  of  a gland, 
feated  on  the  top  of  the  maffeter,  which  is  either 

continuous 


SALIVA. 


Chap.  XYllL 


£94 

continuous  with  the  parotid,  or  diftinct  from  it, 
and  rarely  double ; after  this,  bending  round  the 
tumid  edge  of  the  malfeter,  it  opens  with  an  ab- 
rupt  termination,  without  a papilla,  through  the 
feparatjng  fibres  of  the  buccinator,  furrounded  by 
many  little  glands  of  the  cheek.  The  bulk  of  this 
gland,  and  the  number  of  its  arteries,  render  it  the 
chief  fource  of  the  faliva. 

Dciv.  Another  fmall  gland,  adjacent  to  the  pa- 
rotid, but  twice  as  fmall,  coinpofed  of  fofter  and 
larger  acini,  connected  by  a fimilar  membrane,  is 
contiguous  to  the  corner  of  the  lower  ja»"-bone, 
and  being  in  part  fabcutanepus,  terminates  upon  it, 
and  in  part  fends  off  an  appendix  over  the  inylohy- 
oideus  rnufcle,  which  running  along  the  long  con- 
cave fide  of  the  lower  jaw,  of  a granular  fabric,  and 
fpread  under  the  membrane  of  the  mouth,  is  called 
the  fublingual  gland.  From  the  larger  maxillary 
gland,  a duct  pafies  out  along  with  this  appendix, 
cov^ered  by  the  middle  part  of  the  fublingualis,  from 
which  it  receives  one,  two,  or  three  branches ; by 
whofe  infertion  being  increafed,  it  opens  into  a pro- 
jecting membranous  cylinder,  feated  on  the  bridle 
of  the  tongue.  But  other  fmall  and  fhort  ducts 
from  the  fublingual  gland,  three,  four,  or  more, 
even  to  the  number  of  twenty,  perforate  the  edge 
of  the  tongue  in  the  line  continued  backwards  from 
the  frenum,  with  fhort  little  ducts  and  points,  and 
fecrete  faliva.  There  are  inftances  where  the  lar- 
ger anterior  branch  of  this  gland,  which  ufually 
joins  itfelf  to  the  duct  of  the  maxillary  gland,  goes 
on  fingle,  and  parallel  to  it,  and  opens  by  itlelr. 
Some  other  glands  alfo,  fimilar  to  thofe  of  the 
cheeks,  which  however  may  be  reckoned  among 
the  fubiinguals,  by  their  proper  ducts  perforate  the 
membrane  of  the  mouth  where  it  departs  from  the 
tongue.  Various  other  falival  ducts  have  been  in- 
timated by  difierent  perlons,  but  they  are  not  con- 
firmed by  anatomy. 


Dcy- 


Chap.  XVIII. 


SALIVA. 


29  s 

Dcv.  The  Creator  has  wifely  provided,  that  maf- 
tication  cannot  be  performed,  without  the  falival 
glands  being  comprelfed  by  mechanical  neceflity,  fo 
as  to  difcharge  their  fluids  in  an  increafed  quanti- 
ty. For,  when  the  mouth  is  opened,  the  maxillary 
gland,  being  preffed  by  the  digaftric  and  mylohyoi- 
deus,  throws  forth  a fountain  of  faliva  ; the  parotid 
gland  is  compreffed  by  the  maffeter,  when  fwelled, 
and  by  the  cutaneous  mufcle  of  the  neck  which  lies 
over  it : hunger  has  the  fame  effects  with  mufcular 
preffure,  and  caufes  a flow  of  faliva  into  the  mouth. 

Dcvi.  The  food,  therefore,  being  ground  be- 
tween the  teeth,  with  the  watery  faliva  and  air, 
is  broken  down  into  a foft  fucculent,  figurable 
pulp,  replete  with  elaflic  air,  which  being  heated 
by  its  fituation,  on  account  of  its  elafticity,  perpet- 
ually tends  to  the  dilfolution  of  the  particles 
of  the  food  between  which  it  is  included.  By 
this  procefs,  the  oily  and  aqueous  parts  of  the 
food  are  intermixed  ; the  fmell  and  tafle  of  differ- 
ent ingredients  are  blended  together  ; and,  at  the 
fame  time  that  the  faliva  dilutes  the  filine  parts, 
the  food  becomes  fapid.  Such  particles  as  are  vor 
latile,  are  directly  abiorbed  by  the  bibulous  vef- 
fels  of  the  tongue  and  cheeks,  and  recruit  the 
ftrength,  by  being  reflored  to  the  blood-veffels  and 
nerves. 

Dcvii.  But  the  motions  which  are  neceffary  for 
turning  round  the  food  in  the  cavity  of  the  mouth 
that  it  may  be  introduced  between  the  teeth,  are 
effected  by  the  tongue,  cheeks,  and  lips.  And  ef- 
pecially,  the  tongue  being  at  one  time  expanded,  re^ 
ceives  the  food  into  the  fmall  concavity  in  its  fur- 
face  ; and  being  moved  by  its  proper  powers, 
(ccccL.)  conveys  its  load  to  the  part  dehgned.  At 
another  time,  the  tongue  contrafted,  and  narrow, 
fearches  every  part  of  the  mouth  with  its  tip,  and 
collects  together  the  food  into  one  heap.  At  anoth- 
er time,  by  applying  itfelf  to  the  teeth,  it  draws 

froai 


SALIVA. 


Chap.  XVIII. 


296 

from  the  cavity  of  the  cheeks  the  fluids  or  chewed 
aliments,  and  conveys  them  to  the  pofterior  cavity 
of  the  mouth,  fituated  behind  the  teeth. 

Dcviii.  But  thefe  motions  of  the  tongue  are  like- 
wife  governed  by  the  os  hyoides,  which  is  exten- 
flvely  connected  with  it  by  mufcles  and  membranes, 
and  is  compofed  of  a bafis,  concave  inwardly,  of 
horns  extending  outwardly,  and  terminated  by  a 
thicker  knob,  and  of  oval  cornicles.  When  drawn 
dovrn  by  its  refpeftive  mufcles,  it  carries  back  the 
tongue  at  the  fame  time,  and  alfo  deprefles  the  low- 
er jaw,  if  the  mufcles  of  that  be  relaxed.  Thefe 
powers  are  the  fternohyoideus,  but  arifing  alfo  in 
part  from  the  clavicle,  which  is  extenuated  up- 
wards, and  flriped  with  tendinous  lines : the  fter- 
nothyroideus,  which  is  broader,  and  arifes  from  the 
fame  place,  and  alfo  from  the  upper  rib  j on  deprelf- 
ing  the  cartilage,  into  which  it  is  inferted,  it  necef- 
faiily  forces  the  os  hyoides  connected  with  it,  to  de- 
feend  : it  is  intermixed  wirh  the  hyothyroideus  and 
thyreo-pharyngeus,  and  every  where  intermixed 
with  the  fternohyoideus : the  coracohyoideus,  but 
M'hich  arifes  obliquely  from  the  upper  and  fliorter 
fide  of  the  fcapula,  near  its  notch  ; where  eroded  by 
the  jugular  vein,  it  becomes  tendinous ; with  its 
upper  belly,  it  is  ftraight,  and  pulls  the  os  hyoides 
directly  downwards;  it  is  every  where  blended  with 
the  fternohyoideus,  and  the  hyothyroideus,  which 
is  governed  by  the  former  mufcles. 

Dcix.  Other  powers  elevate  the  os  hyoides,  to- 
rether  with  the  tona;ue.  'fhe  ftvlotrloflus  mufcle, 
luflained  by  a peculiar  ligament  from  the  upper 
jaw*,  which  is  fometimes  fiefiry.  The  ftylohyoideus, 
a weak  mufcle,  often  fplit  for  the  palTagc  of  the  bi- 
venter, and  again  collecded  into  two  portions,  ad- 
hering to  the  tendinous  expanfion  of  the  biventer, 
and  inferted  by  the  one  portion  into  the  bafis  ot 
the  os  hyoides,  and  by  the  other  portion  into  the 
horn,  and  mixed  vvith  the  tendinous  expanfion  of 


Chav.  XVIII.  DEGLUTITION.  <297 

jlie  mylohyoideus.  The  ftylohyoideus  alter,  when 
it  is  prefent,  refembles  the  former,  behind  which  it 
is  placed ; arifing  from  the  tip  of  the  ftyloid  procefs, 
and  inferted  into  the  offa  triticea,  it  anfwers  the 
pnrpofe  of  a ligament  to  fuftain  the  os  hyoides.  All 
thefe  mufcles  draw  the  tongue  back,  and  elevate  its 
lides.  The  mylohyoideus,  ar4fing  from  the  whole 
length  of  the  jaw,  combining  into  one  with  its  com- 
panion, elevates  the  tongue,  and  gives  it  firmnefs 
for  various  motions,  or  elfe  it  depreffes  the  jaw. 
The  geniohyoideus,  accompanying  the  genioglof- 
fus,  pulls  the  tongue  forwards  out  of  the  mouth. 

OCX.  But,  moreover,  the  mufcles  of  the  cheeks 
varioufly  move  and  comprefs  the  food  in  the  mouth. 
Some  carry  it  from  the  cavity  of  the  cheeks  into 
the  cavity  of  the  mouth  behind  the  teeth,  as  the 
buccinator  when  the  mouth  is  fhut.  Others  open 
the  mouth  for  receiving  the  food  ; fuch  as  the 
double  headed  proper  elevator  of  the  upper  lip,  and 
the  elevator  communis  in  part,  the  nafalis  labii  fu- 
perioris,  both  zygomatici,  the  riforius,  tariangularis 
menti,  and  the  depreffor  proprius  anguli  oris,  which, 
arifing  on  each  fide  from  an  excavation  near  the 
locket  of  the  canine  tooth,  is  inferted  into  the  orbi- 
cularis. Others,  again,  fhut  the  mouth,  that  the 
food  received  may  not  fall  out ; fuch  as  the  orbi- 
cularis of  each  lip,  the  proper  depreflTor  of  the  up- 
per lip,  and  the  proper  elevator  of  the  lower  lip, 
- and  the  elevator  communis  in  part.  Of  thefe,  more 
particular  defcriptions  may  be  had  from  profelfed 
fyftems  of  anatomy. 

DC XI.  By  thefe  means  the  food,  mixed  with  and 
foftened  by  the  faliva,  is  collected  from  all  fides, 
behind  the  teeth,  and  is  committed  to  the  tongue, 
expanded  by  the  ceratoglofli  and  geniogloffi,  and 
rendered  a little  concave  by  the  ftylogloffus,  from 
thence  it  is  next  conveyed  to  the  fauces. 

Dcxii.  The  tongue  being  raifed  by  the  hylo- 
glofii,  and  extenfively  applied  to  the  palate,  firft 

with 


DEGLUTITION. 


Chap.  XVIII. 


5.98 

with  its  apex,  then  gradually  with  its  pofterior  ex- 
tremity, preffes  the  food  towards  the  fauces,  at  that 
time  the  only  open  paffage.  After  this,  the  thick 
root  of  the  tongue  itfelf  refifts  the  larynx,  which  is 
drawn  upwards,  and  preffes  down  the  approaching 
epiglottis,  which  Hands  up  behind  the  tongue,  and 
is  connefted  with  it  by  numerous  membranes,  and 
perhaps  by  fome  muicular  fibres.  At  the  fame 
time,  all  the  mufcles  elevating  the  pharynx  ad;  to- 
gether } the  biventer,  geniohyoideus,  geniogloffus, 
ftylohyoideus,  ftylogloffus,  ftylopharyngeus,  and 
others,  and  draw  the  larynx  upwards  and  fonvards, 
fo  that  the  epiglottis  prefents  itfelf  oppofite  to  the 
tongue,  and  is  more  eafily  inclined.  Hence  it  is 
neceffary  for  deglutition,  that  the  jaws  be  clofed,  or 
at  leaft  that  the  lower  one  be  raffed,  and  fixed  in 
that  pofition,  that  the  biventer,  and  the  other  muf- 
cles already  mentioned,  may  derive  ftability,  from 
it,  and  elevate  the  os  hyoides.  Thus  tl»e  epiglottis, 
being  turned  down,  fhuts  up  the  pail'age  to  the 
larynx  fufficiently  and  largely,  and  over  it,  as  over 
a bridge,  the  food  paffes  into  the  fauces. 

Dcxiii.  By  the  pharynx  we  underhand  an  ample 
Ihapelefs  cavity,  bounded  behind  by  all  the  vertebr'e 
of  the  neck,  and  the  occipital  bone  before  the  hm.i- 
men  magnum,  in  the  middle  by  the  cuneiform  bo^  e, 
and  before  by  the  opening  of  the  nares,  the  move- 
able  velum  of  the  palate,  tlie  niouth,  ' he  tongue, 
and  the  larynx  : below  it  is  continued  int-'  tlie  cUb- 
phagus.  Its  fides  are  formed  by  the  low  . i.;w,  the 
cheeks,  the  velum  of  the  palate,  the  pterygoid  pro- 
ccfs,  the  ftiliform  appendix,  the  tongue,  os  hyoides, 
and  larger  cartilages  of  the  larynx.  It  forms  one 
foft  membranous  bag,  outwardlv  furrounded  on  all 
fiaes  by  mufcular  fibres.  Its  internal  meiribrane  is 
continuous  with  the  cuticle,  and  renewable,  but 
more  moiff . Outwardly  the  pharynx  is  covered  by 
a good  deal  of  cellular  fubftance,  more  efpecial'iy  in 
its  pofterior  and  bteral  parts.  Therefore  it  is  lax 


Chap.  XVIII. 


DEGLUTITION. 


299 

and  dilatable,  and  fitted  for  receiving  all  bodies 
that  are  prefled  by  the  tongue  over  the  larynx. 

Dcxiv.  It  is  dilated  in  the  action  (dcxii.)  by  the 
powers  elevating  it,  by  the  ftylopharyngeus,  which 
defcends  fometimes  double  into  the  membrane  of 
the  larynx,  under  the  os  hyoides,  and  into  the  mar- 
gin of  the  thyroid  cartilage,  and  is  largely  diftribu- 
ted  over  the  internal  furface  of  the  pharynx,  togeth- 
er with  the  following  mufcle  ; the  thyreopalatinus, 
fpread  in  the  form  of  an  arch  round  the  moveable 
palate,  and  forming  two  columns,  which  defcend 
along  the  fides  of  the  pharynx,  and  form  a confid- 
erable  part  of  that  bag,  being  alfo  connefled  by 
broad  fibres  to  the  thyroid  cartilage.  That  the 
falpingopharyngeus  is  a true  mufcle,  I am  ready  to 
believe,  rather  from  the  obfervations  of  eminent 
anatomifts  than  from  my  own.  Of  the  cephalo- 
pharyngeus,  I am  doubtful,  unlefs  you  reckon  the 
ftrong  white  cellular  fubftance,  which  occupies  the 
tipper  part  of  the  pharynx,  as  a mufcle.  Drink 
pafles  round  the  larynx  on  each  fide  of  the  epiglot- 
tis, and  falls  into  the  oefophagus. 

Dcxv.  The  aliments  are  prevented  from  regurgi- 
tating into  the  noftrils  when  they  arrive  at  the  dila- 
ted pharynx  (dcxiv.)  by  the  palatum  mobile,  which 
is  interpofed.  Anteriorly  from  the  bony  palate,  and 
laterally  from  the  pterygoid  wings,  is  continued  a 
moveable  velum,  compoied  of  the  membranes  of  the 
mouth  and  noftrils,  with  intervening  mufcles  and 
glands,  almoft  of  a fquare  figure,  and  hanging  be- 
twixt the  cavity  of  the  nares  and  mouth,  into  the 
hollow  fauces,  in  fuch  a manner  that  it  naturally 
Reaves  the  former  open,  and  is  concave  towards  the 
mouth  : the  middle  lower  portion  of  this,  extended 
into  a conical  lhape,  pendulous,  before  the  epiglot- 
tis, and  replete  with  many  glands,  from  its  appear- 
ance in  a difeafed  ftate,  is  called  the  uvula.  At  each 
fide  of  the  velum,  two  arches  defcend  from  the  ve- 
lum palati,  of  which  the  fmaller  and  thinner  goes 

to 


DEGLUTITION.  Chap.  XVIIL 


to  the  tongue,  the  larger  to  the  pharynx.  The  ele- 
vator of  this  velum,  which  is  llrong,  arifes  from 
the  afperities  and  plane  furface  of  the  os  petrofum, 
behind  the  fpinal  foramen,  and  alfo  from  the  cartil- 
age of  the  Euftachian  tube,  defcends  inwards  with 
its  companion,  forms  an  arch  in  the  velum  mobile, 
between  the  two  plates  of  the  thyreopalatinusmufcle. 
It  may  therefore  draw  that  velum  to  the  nares  and 
tubes,  that  the  food  may  not  enter  either  of  them. 
But,  during  deglutition,  it  does  not  feem  to  have 
any  confiderablc  acHon.  At  this  time  regurgitation 
into  the  noftrils  is  prevented  by  the  conftri&on  of 
the  mufcles  of  the  pharynx,  together  with  the  de- 
preffion  of  the  thyreopalatinus,  which  manifeftly 
draws  the  moveable  velum  downwards,  and  applies 
it  to  the  tongue  and  pharynx,  and  of  the  circum- 
flcxus  palati  mollis,  which  arifing  a little  more  for- 
wards from  the  fame  petrous  bone,  and  from  the 
Iharp  procefs  of  the  cuneiform  wing,  and  from  the 
interval  between  the  wings  and  iiinermoft  wing, 
and  from  the  cartilage  of  the  Euftachian  tube,  dc- 
fcends  broader  ; and,  pahlng  through  the  notch  of 
the  pterygoid  hook,  it  changes  its  direction,  and 
afcends  with  a radiated  tendon,  difperfed  through 
the  upper  membrane  of  the  velum  palati,  and,  join- 
ing with  its  fellow,  forms  the  balls  of  the  other 
niufcles,  and  adheres  to  the  fmooth  edge  of  the  pal- 
ate bone.  This  is  able  both  to  open  the  tube,  and 
Jeprefs  the  velum  mobile,  Thus  t;\e  pharynx  be- 
ing contracted  like  a fphincter,  fo  xes  down  the 
food,  without  permitting  any  part  to  regurgitate  in- 
to the  nares.  Hence,  when  the  veiu:n  of  the  palate 
is  injured,  the  aliments  regurgitate  into  the  noftrils, 
and  deafnefs  enfues. 

Dcxvi.  During  the  effort  to  deprefs  the  food 
(dcxvii.)  the  velum  being  placed  upon  it,  and 
depreffed,  is  drawn  down  towards  the  tongue  by 
the  palatopharyngei,  and  by  the  circumflcxus  pa- 
lati mollis.  Thefe  mufclcs,  together  wdth  the  glof- 

fopalatiuus. 


Chap.  XVIH.  DEGLUTITION.  30! 

fopalatinus,  (which  laft  is  indeed  weak,  is  received 
into  the  lelfer  arch  of  the  fauces,  and  on  the  one 
lide  fs  united  with  its  companion  into  an  arch  in 
the  velum  of  the  palate,  and  on  the  other  is  inferr- 
ed into  the  tongue,)  prefs  the  velum  againk  the 
protuberant  root  of  the  tongue,  and  intercept  any 
return  to  the  mouth.  After  the  danger  of  any  part 
falling  into  the  windpipe  is  over,  the  epiglottis  is 
raifed  up  again,  both  by  its  own  elafticity,  and  by 
the  tongue  itfelf  being  again  drawn  forwards.  Laft- 
ly,  the  deprefled  uvula  is  raifed  by  the  azygos,  which 
arifes  from  the  tendons  of  the  circumflexus,  and  by 
the  levator  of  the  foft  palate. 

Dcxvii.  A little  after  this,  follows  an  effort  to 
urge  the  food  downwards,  which  is  exerted  by  the 
conftridtors  of  the  pharynx,  which  draw  the  back 
part  forwards  ; thefe  mufcles  are  partly  tranfverfe, 
and  partly  afcend.  into  the  pofterior  furface  of  the 
pharynx.  The  principal  is  the  pterygopharyngeus, 
arifing  from  the  whole  hook,  and  from  the  edge  of 
the  internal  wing,  and  from  the  tendon  of  the  cir- 
cumflex mufcle  ; from  whence  forming  an  arch, 
it  is  extended  upwards  and  backwards,  and,  largely 
furrounding  the  upper  part  of  the  pharynx,  it  unites 
with  its  cognominal  companion.  The  mylopharyn- 
geus  is  partly  continuous  with  the  fibres  of  the 
buccinator,  in  the  middle  betwixt  its  two  adhefions 
to  the  bones,  and  partly  arifes  from  an  origin  of  its 
own,  above  the  laft  of  the  grinders  in  the  lower 
jaw.  Thefe  being  almoft  tranfverfe,  and  furround- 
ing the  pharynx,  draw  its  back  part  forwards. 
Next  follow  the  afcending  mufcles  in  two  ftrata, 
the  geniopharyngei,  of  w'hich  the  obfcure  and  con- 
fufed  fibres  originate  from  the  tongue  ; the  chon- 
dropharyngei,  of  a triangular  figure,  arifing  from 
the  officula  trkicea  ; the  ceratopharyngei,  which 
afcend  radiated  from  half  of  the  horn  ; the  fyn- 
defmopharyngei,  arifing  from  the  horn  of  the  thy- 
roid cartilage,  and  diftindl  from  the  following  ; the 

double 


5^2  DEGLUTITION.  Chap.  XVIII. 

double  thyreopharyngei,  increafed  by  fibres  of  the 
ilernothyroideus  and  cricothyroideus,  and  the  tranf- 
verfe,  the  afcending,  and  the  defcending  crycbpha- 
ryngei.  Thefe  mufcles  act  focceffively,  the  upper- 
moft  firft,  and  then  according  to  their  fituation, 
and  force  the  food  into  the  cefophagus.  At  the 
fame  time,  the  depreffing  mufcles  of  the  larynx, 
the  coracobyoideus,  fternohyoideus,  and  fternothy- 
roideus,  draw  down  the  larynx  backwards,  com- 
prefs  the  pharynx  and  urge  the  food  downwards. 
The  arytenoidsei  contract  the  perpendicular  chink 
of  the  larynx  as  the  food  pafl’es  near  it. 

Dcxviii.  As  various  dry  and  rough  bodies  are 
fometimes  fwaUowed,  and  as  it  was  neceffary  for 
the  pharynx  to  be  dilatable  and  indolent,  the  great 
quantity  of  mucus,  which  is  collected  in  all  parts 
of  the  fauces,  is  of  great  importance.  Therefore, 
in  general,  betwixt  the  nervous  and  innermoft  coat 
of  the  pharynx,  are  placed  a very  great  number  of 
limple  oval  follicles,  which  pour  out  through  Ihort 
mouths  a bland,  aqueous,  but  vifcid  and  ropy  mu- 
cus, having  a greater  quantity  of  oil,  volatile  fait 
and  earth,  than  the  faliva.  They  are  molt  plenti- 
ful in  that  part  of  the  pharynx  which  is  extended 
under  the  occipital  bone,  where  they  are  difpofed 
in  a fort  of  radiated  right  lines  ; and  about  the  ton- 
fil  towards  the  Euftachian  tube,  where  commonly 
the  fecond  tonlil  lies  on  each  fide  adjacent  to  the 
large  one,  and  in  that  portion  of  mufele  which  is 
called  falpingopharyngeus.  But  likewife  many  flat 
and  circular  follicles  of  this  kind  are  feated  on  the 
back  part  of  the  tongue,  as  far  as  the  foramen  cae- 
cum (cGocxLvin.)  Other  pores  from  the  pulpy 
flefli  of  the  palate,  and  from  the  numerous  glands 
lituated  there,  difeharge  a llmilar  mueus.  JNIore- 
over,  the  whole  moveable  palate  is  of  a glandular 
nature  like  the  pharynx ; only  compofed  of  more 
numerous  and  thickly  diftributed  follicles.  Nor, 

iaftly. 


Chap.  XVIIL  DEGLUTITION.  303 

laftly,  are  lacunx  wanting,  into  each  of  which  ma- 
ny fimple  glands  unite. 

DC XIX.  Where  the  pharynx  defcends  from  the 
pterygoidal  hook  betwixt  the  two  arches  of  the 
fauces,  diat  is  between  the  gloffopalatinus  and  pha- 
ringopalatinus,  are  feated  the  tonfils,  one  on  each 
fide,  of  an  oval  figure,  convex  behind,  and  thicker 
on  the  upper  part,  perforated  inwardly  with  ten  or 
more  large  finufes,  which  open  through  the  mem- 
branous velum,  and  by  the  preflure  of  the  adjacent 
mufcles  difcharge  a great  quantity  of  a very  vifcid 
mucus  from  their  finufes.  In  like  manner,  the  ad- 
jacent parts  of  the  nares,  and  tumid  ring  of  the 
tubes,  and  the  furface  of  the  epiglottis  next  to  the 
larynx,  and  the  back  of  the  arytenoid  cartilages, 
are  replenifhed  with  mucous  organs.  Laftly,  the 
cefophagus  itfelf,  on  all  fides,  abounds  with  fimple 
follicles,  from  which  a mucus  more  fluid  is  poured. 
The  glandulx  oefophagex  are  of  the  conglobate 
kind,  and  contribute  nothing  to  this  mucus.  The 
blood- veflels  of  the  tonfils  come  from  thofe  of  .the 
tongue  and  lips  ; thofe  of  the  pharynx  from  thefe 
and  from  the  pharyngea  ; thofe  of  the  cefophagus 
from  the  pharyngeals,  upper  and  lower  thyreoi- 
dals,  the  bronchials  and  aorta.  The  numerous  veins 
of  the  palate  and  tonfils,  after  forming  plexufes, 
meet  in  the  fuperficial  branch  of  the  internal  jugu- 
lar. 

Dcxix.  The  cefophagus  is  a double  tube,  of  which 
the  interior  is  feparated  from  the  exterior,  by  much 
inflatable  cellular  fubftance.  The  interior  is  ner- 
vous and  ftrong,  continuous  with  the  membranes 
of  the  mouth  and  nares,  and  feparated  from  the 
innermoft,  (which  is  the  epidermis,  plaited  and  po- 
rous, but  not  villous,  exhaling  a thin  fluid  and  pul- 
py,) by  peculiar  fliort  cellular  fubftance,  in  which 
veflels  are  reticulated,  and  glands  are  interfperfed, 
which  are  continuous,  and  fimilar  to  thofe  of  the 
pharynx.  The  exterior  tube,  the  mufcular,  is  alfo 

ftrong,- 


DEGLUTITION. 


Chap.  XVIII. 


ftrong,  with  fibres  continued  backwards  and  down- 
wards from  the  cricoid  cartilage,  changing  from 
annular  into  external  longitudinal  fibres,  railing 
the  cefophagus  againft  the  food,  and  dilating  it 
that  the  mouthful  may  be  received.  But  other 
internal  circular  fibres,  which  are  alfo  ftrong,  arife 
in  like  manner  from  the  cricoid  cartilage,  and  by 
their  fuccefiive  contraction,  force  the  food  down 
through  the  long  tube  of  the  cefophagus,  which  de- 
fcends  firft  in  a direct  courfe,  a little  to  the  left  fide 
of  the  windpipe  ; in  the  breaft,  it  paftes  behind  the 
heart,  through  the  pofterior  interval  between  the 
two  bags  of  the  pleura  (lxxvii.)  from  whence  it  in- 
clines by  degrees  a little  to  the  right,  and  then  for- 
wards, that  it  may  pafs  through  the  appointed 
opening  in  the  diaphragm  (cclxii.)  in  the  inter- 
val between  exfpiration  and  infpiration.  The 
whole  cefophagus  is  furrounded  externally  by  cel- 
lular fabftance,  by  which  it  is  loofely  tied  to  the 
neighbouring  parts. 

ncxx.  The  aliments  are  moved  tlirough  the  cefo- 
phagus as  through  an  inteftinc.  The  longitudinal 
fibres,  afcending  to  the  cartilages  of  the  larjmx, 
dilate  the  gullet,  to  receive  the  dcfcending  morfel. 
But  when  it  is  received  into  the  gullet,  the  longi- 
tudinal fibres  in  like  manner  dilate  and  elevate  the 
gullet  to  that  place  which  has  received  it.  Then 
that  part  of  the  cefophagus,  where  the  morfel  is 
feated,  being  irritated,  contracts,  and  propels  the 
food  downwards.  Its  mufcularity  is  ftrong,  and 
very  irritable. 

Dcxxi.  This  upper  opening  of  the  ftomach  is 
contracted,  by  the  action  of  both  the  lower  mufcles 
of  the  diaphragm,  in  infpiration,  and  the  food  is 
confined  within  the  ftomach,  fo  that  every  preflure 
of  the  diaphragm  fends  it  naturally  towards  the 
pylorus.  By  this  means,  the  ftomach  is  fo  clofely 
ftaut,  that  in  perfect  health,  even  vapours  are  con- 


STOMACH. 


Chap.  XIX. 


30s 


fined  within  the  ftomach  j and  do  not  afc£nd  but 
from  a morbid  afFedion. 


CHAP.  XIX. 

ACTION  OF  THE  STOMACH  ON  THE  FOOD. 

Dcxxii.  ^T^HE  ftomich  is  a membranous  bag,  def- 
I tined  for  the  reception  of  the  food  ; 
placed  within  the  abdomen,  behind  the  liver,  dia- 
phragm and  left  falfe  ribs  ; of  a figure  fomewhat 
Oval,  or  like  a calk ; longeft  tranfverfely,  and  the 
more  fo  the  more  aged  the  perfon  is.  In  the  foetus, 
it  is  altogether  round  and  fliort.  But  if  we  confid- 
er  its  figure  more  accurately,  every  fedion  of  it  is 
circular  j but  fo,  that,  in  its  left  extremity,  there 
is  an  an  impervious  cavity  obtufely  conical,  from 
whence  the  ftomach  gradually  grows  wider,  and  its 
fedions  increafe  tov/ards  the  cefophagus,  at  whofe 
infertion  is  its  largeft  fedion ; from  thence  it  di- 
miniflies  flowiy,  till  being  refleded  towards  itfelf,  it 
ends  in  the  pylorus.  Its  bulk  depends  in  a great 
meafure  on  the  quantity  of  food,  by  which  the  ca- 
vity of  the  ftomach  is  augmented  ; and,  on  tlie 
contrary,  it  is  diminiftied  by  falling.  Its  fituation 
in  general  is  tranfverfe  ; yet  fo  that  the  entrance  of 
the  cefophagus  is  pofterior,  and  its  right  termina- 
tion anterior.  The  middle  of  the  human  body,  or 
enfiform  cartilage,  correfponds  nearly  to  the  centre 
of  the  ftomach  ; but  alfo  to  its  right  fide,  and  laft- 
ly  to  the  pylorus : to  the  latter  the  umbilical  fif- 
fure  correfponds.  Since  its  figure  is  round,  but  in- 
curvated ; when  empty,  its  larger  convex  arch  is 
pendulous  ; but  when  full,  it  appears  prominent 
forwards  within  the  peritonaeum.  At  that  time, 
the  leffer  arch,  interpofed  between  the  two  orifices, 
is  direded  perfedly  backwards,  and  includes  the 
W fmail 


STOMACH. 


Chap.  XIX. 


306 

fmall  lobe  of  the  liver.  The  infertlon  of  the  oefo- 
phagus  in  the  full  ftomach  is  more  horizontal ; but 
in  the  empty  ftomach,  more  perpendicular  ; the 
right  extremity  of  the  ftomach,  when  empty,  is 
bent  upwards  to  the  pylorus ; in  the  fuU  ftomach, 
it  is  bent  backwards,  and  therefore  defcends  in  per- 
fons  lying  on  their  back.  In  man,  when  alive,  the 
fituation  of  the  ftomach,  approaches  nearer  to  that 
which  we  have  attributed  to  the  full  one. 

Dcxxiii.  The  vifcera,  contiguous  to  the  ftomach, 
are  the  fpleen,  contiguous  to  its  left  imperforated 
extremity,  and  connected  with  it  by  much  omen- 
tum ; the  lobule  of  Spigelius,  filling  up  its  Idler 
curvature  ; the  left  lobe  of  the  liver,  largely  inter- 
pohng  itfelf  betwixt  the  ftomach  and  the  dia- 
phragm, and  comprefling  the  anterior  part  of  the 
ftomach  ; after  which,  below  the  liver,  a moderate 
portion  of  the  ftomach  is  immediately  contiguous 
to  the  diaphragm,  which  there  lies  under  the  falfe 
ribs,  or  it  is  entirely  covered  : behind,  the  pan- 
creas lies  under  it ; below  it  when  empty,  the  tranf- 
verfe  portion  of  the  colon  is  contiguous  for  a con- 
liderable  way ; laftly,  from  the  leffer  curvature,  arifes 
the  little  omentum,  from  which  a continuous,  but 
Itronger  membrane,  connects  the  oefophagus  with 
the  diaphragm  : and  the  larger  omentum  rs  not 
connected  to  the  whole  length  of  the  ftomach,  but 
is  wanting  on  the  right  fide  near  the  pylorus ; and 
on  the  left,  it  is  continued,  into  a ligament,  which 
connects  the  fpleen  and  alfo  the  diaphragm  with  the 
ftomach.  The  ligaments  are  productions  of  the 
peritonxmn,  receding  from  the  diaphragm,  thrown 
over  the  ftomach,  and  forming  is  outermoft  coat. 
Of  the  orifices,  the  pylorus  lies  farther  forwards, 
more  to  the  right  fide,  and  a little  lower. 

Dcxxiv.  The  fabric  of  the  ftomach,  in  general, 
is  the  fame  with  that  of  the  oefophagus  ; of  which , 
it  is  a kind  of  expanfion  ; and,  in  fome  animals, 
perfectly  fimihr.  The  outermoft  coat  is  from  the 

peritonceum  j 


Cpiap.  XIX. 


STOMACH. 


307 

peritonseum  ; is  ftrong,  limits  the  reft,  and  affords 
fupport  to  the  fubjacent  mufcular  fibres : it  is  ex- 
panded into  both  omcntums ; and  in  that  place,  the 
ftomach  is  without  its  outermoft  coat.  Then  fol- 
lows the  firft  cellular  coat,  more  abundant  at  the 
origin  of  the  little  omentum,  where  it  contains  con- 
globate and  lymphatic  glands,  and  alfo  in  the  re- 
gion of  the  great  omentum  j it  is  thinner  and  fliort- 
er  in  the  intermediate  planes,  fo  that  the  outer  and 
mufcular  tunic  in  them  cohere  together  : in  this 
fubftance,  the  large  branches  of  the  veflels  are  dii- 
tributed. 

Dcxxv.  The  mufcular  coat  is  next  in  order,  which 
is  complex  and  difficult  to  defcribe  or  prepare. 
The  longitudinal  fibres  of  the  oefophagus,  when 
they  arrive  at  the  ftomach,  diftribute  themfelves 
along  all  the  fides  of  the  ftomach.  Some  of  them, 
of  confiderable  ftrength,  run  on  to  the  pylorus, 
along  the  fmaller  curvature  ; part  of  which,  by  de- 
grees declining,  and  following  the  length  of  the 
ftomach,  defeend  into  the  planes  of  each  fide,  and 
part  of  them  proceed  along  the  pylorus  into  the 
duodenum  itielf,  and  gradually  disappear.  Other 
fimilar  fibres^  which  are  lefs  ftrong,  defeend  to  the 
blind  fack  on  the  left  fide  of  the  ftomach.  Befides, 
other  fibres  furround  that  blind  fack,  w'hich  being 
gradually  increafed,  are  continued  with  the  circu- 
lar fibres  of  the  reft  of  the  ftomach.  This  fecond 
ftratum  of  fibres  is  the  moft  confiderable.  Laftly, 
the  fphinder  of  the  cefophagus,  is  the  moft  inter- 
nal, and  is  a continuation  of  the  annular  fibres  of 
the  cefophagus.  It  is  compofed  of  fibres,  arifing 
from  the  left  of  the  cefophagus,  and  running  to  the 
right,  on  each  fide  of  the  gullet,  which  they  nearly 
furround  ; and  gradually  becoming  longitudinal, 
they  terminate,  covered  by  the  fecond  ftratum.,  near 
the  pylorus.  The  ligaments  of  the  pylorus  are  two 
bands,  lying  betwixt  the  two  curvatures,  which 
cor.trad:  the  pylorus.  They  are  formed  of  longi- 
w 2 tudinal 


STOMACH. 


Chap.  XIX. 


3°S 

tudinal  fibres,  and  run  from  the  ftomach  to  the  py- 
lorus, intimately  connected  with  the  external  mem- 
brane. 

DC  XXVI.  Next  to  the  mufcular  fibres,  there  is 
the  fecond  cellular  coat,  larger  than  the  firft,  eafily 
inflatable,  fofter,  and  confifting  of  larger  cells  than 
is  common  in  the  inteflines.  Into  it,  the  veflels, 
which  perforate  the  mufcular  coat,  enter  with  large 
trunks,  and  are  divided  into  an  angular  network. 
Under  this,  lies  the  nervous  coat,  which  is  thick, 
white,  and  firm  ; and,  like  other  nersmus  coats, 
properly  conftitutes  the  true  fubftance  of  the  fto- 
roach.  Then  the  third  cellular  ftratum,  which  is 
fufficiently  evident,  and  whofe  vafcular  network 
is  compofed  of  fmaller  velfels  than  the  former  re- 
ticulation. Then  the  villous  coat,  continuous  with 
the  external  cuticle,  reparable  ; mucous  and  foft, 
with  very  lliort  villi,  but  folded  into  large  wrin- 
kles, ftellated  under  the  oefophagus,  and  in  the  mid- 
dle of  the  ftomach  almoft  parallel  vdth  the  ftomach 
itfelf.  But,  at  the  extremity  of  the  pylorus,  there 
is  a more  confiderable  fold,  commonly  called  its 
valve,  formed  of  tranfverfe  fibres,  and  of  a redu- 
plication of  the  nervous  coat  thickened,  and  of  the 
villous,  fo  that  a kind  of  tumid  ring  is  produced, 
flippery  and  flefliy,  which  is  furrounded  by  the  du- 
odenum for  a conftderaljie  length.  The  large  wrin- 
kles of  the  villous  membrane  are  finally  fubdivided 
into  fmaller  ones,  refembling  a reticulation,  of  a 
quadrangular  figure,  flvallow,  eafily  difappearing, 
and  more  obfcure  than  thofe  in  the  biliary  duels. 
Tliroucrhout  the  whole  of  this  villous  coat,  but 
more  efpecially  towards  the  pylorus,  I have  certain- 
ly obferved  fome  pores,  not  always  to  be  perceived, 
which  terminate  in  fimple  follicles,  feated  in  the 
third  cellular  ftratum. 

Dcxxvii.  The  veflels  of  the  ftomach  are  numer- 
ous, and  derived  from  many  trunks,  that  the  alflux 
of  the  blood  might  not  be  intercepted  by  any  prel- 

fure. 


Chap.  XIX. 


STOMACH. 


309 

fure,  which  might  ealily  have  happened  if  there  had 
been  a fingle  trunk.  The  common  fource  of  all 
thefe  is  the  cceliaca ; from  its  tripod,  or  above  the 
faid  diviiion,  arifes  its  firft  and  largeft  artery,  the 
upper  coronary,  with  one  branch  furrounding  the 
ceiophagus  ; to  which,  and  to  the  diaphragm,  and 
alfo  to  the  liver,  it  gives  branches ; with  another 
following  the  fmaller  curvature,  it  inofculates,  by 
an  anterior  and  pofterior  trunk,  with  the  lefTer  co- 
ronary on  the  right  fide,  which  arifes  from  the 
right  branch  of  the  cceliac  in  the  vena  portarum  it- 
felf,  and  returns  along  the  fmaUer  curvature.  But 
the  fame  right  branch  of  the  cceliac,  after  defcend- 
ing  behind  the  origin  of  the  duodenum,  gives  off  a 
confiderable  artery  to  the  great  arch  of  the  ftomach, 
the  right  gaftro-epiploica,  which  being  fufpended 
in  the  omentum,  fupplies  both  furfaces  of  the  fto- 
mach, and  furrounding  the  greater  part  of  it,  it  is 
inferted  into  the  left  gaftro-epiploica.  Namely,  the 
left  trunk  of  the  cceliac,  as  it  paffes  along  the  du<ft 
of  the  pancreas  and  finuofity  of  the  fpleen,  fuccef- 
fively  fends  off  many  branches  to  the  ftomach  : of 
which  the  firft  are  commonly  namelefs  ; and  of 
the  following,  one  branch,  called  the  left  gaftro- 
epiploica,  fends  off  one  confiderable  branch,  and 
other  fmaller  branches,  to  the  omentum,  and  re- 
turns round  the  ftomach  to  the  right  fide,  to  inof- 
culate  with  its  companion  of  the  right  fide.  Other 
fmaller  twigs,  coming  from  thofe  of  the  fpleen,  are 
fpread  upon  the  remaining  part  of  the  greater  curve 
of  the  ftomach,  as  far  as  the  diaphragm,  and  are 
called  the  vafa  brevia.  Frequently,  alfo,  one  or 
two  arteries  come  from  the  fplenic  one,  to  the  pof- 
terior furface  of  the  ftomach  under  the  cefophagus, 
in  a different  direction  from  the  gaftro-epiploics. 
The  other  arteries  are  fmaller,  the  upper  pylorics 
from  the  hepatics,  and  the  lower  from  the  gaftro- 
epiploics,  and  thofe  of  the  loweft  part  of  the  cefo- 
phagus from  the  phrenic  arteries. 


DCXXVIII. 


310 


STOMACH. 


Chap.  XIX. 


Dcxxviii.  Thofe  arteries  are  diftributed  in  the 
following  manner ; the  external  and  mufcular  mem- 

O 

branes  receive  Ihort  branches  ; the  trunks  are  ar- 
ranged in  the  firft  cellular  ftratum,  and  with  little 
diminution  penetrate  the  mufcular  coat ; and  be- 
tween that  and  the  nervous  membrane,  they  com- 
pofe  a larger  and  true  network  ; in  which  aU  the 
fmall  arteries  of  the  different  trunks  are  united,  by 
an  infinity  of  inofculations.  From  this  reticulation, 
again,  other  fliort,  but  numerous  and  fmall  ramifi- 
cations, go  to  the  third  cellular  and  villous  coat  of 
the  ftomach. 

Dcxxix.  The  branches  of  the  veins  accom.pany 
the  arteries.  The  greater  coronary  generally  goes 
to  the  left  trunk  of  the  porta,  together  vdth  the 
brevia  and  left  gaftro-epiploic  ; while  the  right  A'ein 
of  the  fame  denomination  joins  with  the  middle 
vena  colica,  and  is  inferted  along  with  it  into  the 
mefenteric  branch  of  the  A’’ena  portarum.  Finally, 
the  right  coronary  vein  belongs  to  the  trunk  of  the 
vena  portarum  itfelf.  All  thefe  veins  are  without 
valves ; and  the  upper  coronary  veins  inofculate 
with  the  branches  of  the  vena  fine  pari,  in  like  mian- 
ner  as  the  arteries  inofculate  with  the  thoracic  cefo- 
phagei. 

Dcxxx.  The  nerves  of  the  ftomach  are  large  and 
numerous,  produced  from  the  eighth  pair,  which 
forms  two  plexufes  on  the  oefophagus,  of  which  the 
anterior  and  fmaller  goes  from  the  oefophagus  to 
the  greater  curvature  and  anterior  furface  ; and  the 
pofterior  and  larger  to  the  fmaller  curvature,  and 
along  with  the  arteries  to  the  liver,  and  to  the  pan- 
creas and  diaphragm  itfelf.  Thefe  nerves  m.ay  be 
traced  into  the  fecond  cellular  ftmtum.  Beyond 
this,  efpecially  the  papillae,  are  more  obfcure.  From 
their  very  great  number,  the,  ftomach  is  extremely 
fenfible,  efpecially  about  the  entrance  of  the  gullet, 
infomuch,  that  acrimonies,  wiiich  are  not  perceived 
by  the  tongue,  turn  the  ftom.ich  j the  inteftines  are 


STOMACH. 


Chap.  XIX. 


3” 


alfo  known,  by  certain  morbid  obfervations,  to  be 
much  more  indolent ; even  the  naked  fkin  itfelf  is 
lefs  fenfible  than  the  ftomach.  By  making  a liga- 
ture upon  the  nerves  of  the  eighth  pair,  the  adion 
of  the  ftomach  and  the  digehion  of  food  are  de- 
ftroyed. 

DC XXXI.  I have  feen  confiderable  lymphatic  vef- 
fels  in  the  fmaller  curvature  of  the  ftomach,  ariftng 
from  its  glands,  and  infer  ted  by  a very  large  trunk 
into  the  thoracic  du6l.  Others,  without  doubt, 
arife  from  the  glands  of  the  fame  kind  in  the  great- 
er curve  5 and  eminent  anatomifts  have  obferved 
lymphatic  glands  over  the  whole  ftomach.  Other 
lacteal  veflels,  I have  not  feen,  and  wall  not  readily 
admit  thofe  lately  defcribed,  which  are  faid  to  pafs 
from  the  ftomach  through  the  omentum  to  the  liv- 
er, filled  with  true  chyle. 

DC XX XII.  All  bags  in  man  are  perforated  by  in- 
organic pores  ; through  thefe,  water  poured  into  the 
ftomach  exudes  through  it  when  ftiut,  and,  on  the 
contrary,  penetrates  into  the  cavity  of  the  ftomach 
when  put  under  water.  But  we  cannot  for  this 
reafon  conclude,  that  during  life  this  paffage  is  per- 
vious to  moifture. 

Dcxxxiii.  Within  the  human  ftomach,  we  firft 
meet  with  a great  quantity  of  mucus,  anointing  its 
villous  coat,  derived  from  the  pores  before  defcrib- 
ed (dcxxvi.)  which  mucus  is  not  unfrequently  ting* 
ed  by  regurgitated  bile.  Befides,  from  the  fto- 
mach, after  fafting,  upon  bending  the  body,  a lim- 
pid humour  will  frequently  flow,  poflefilng  all  the 
properties  of  the  faliva,  but  more  mucous,  which  it 
is  very  difficult  to  obtain  pure  in  the  ftomach.  It 
is  entirely  without  any  acidity,  when  it  can  be  had 
unmixed  with  food.  When  feparated  from  the 
acid  impregnations  of  the  food,  and  left  to  itfelf,  it 
changes,  both  in  man  and  brutes,  rather  to  an  alka- 
line nature,  more  efpecially  in  a fafting  animal. 
This  liquor  diftils  from  the  arteries  of  the  ftomach, 

through 


DIGESTION. 


Chap.  XIX. 


3*12 

through  its  villous  coat,  as  is  proved  by  anatomical 
injections ; by  which  water,  glue,  and  oil,  may  be 
thrown  into  the  ftomach,  through  numberlefs  pores. 

Dcxxxiv.  Then  it  muft  be  rem.embered,  that 
the  ftomach  is  comprefled  as  in  a prefs  in  the  ab- 
domen, which  is  perfedly  full,  between  the  dia- 
phragm, of  which  the  concave  left  wing  lies  before 
and  above  the  liver,  and  therefore  over  the  fto- 
mach,  and  the  renfting  mufcles  of  the  abdomen, 
the  rectus  and  obliqui,  but  chiefly  the  tranfverfe. 
The  more  the  ftomach  is  filled,  the  more  it  ex- 
periences this  preflure  of  the  abdomdnal  mufcles  j 
becaufe,  at  that  time,  it  is  in  contact  with  the  perU 
tonasum  at  a rio;ht  angle. 

O O 

Dcxxxv.  Now  we  muft  explain  v'hat  is  received 
into  the  ftomach,  and  why  it  is  received.  The 
Creator  has  giv'en  to  man  pain  (dlxiv.)  and  plea- 
fure,  for  his  prefervation  ; the  one  to  incite  him  to 
avoid  evil,  the  other  to  imdte  him  to  ufeful  actions. 
But  the  taking  of  aliment  is  of  the  greateft  necef- 
ftty  to  man.  For  fince  every  day  there  is  much 
perfpired,  much  wafted  of  his  real  fubftance,  he 
alfo  ftands  in  need  of  reparation  ; as  the  body  is 
manifeftly  wafted  by  fafting.  But  the  neceflity 
of  taking  food  is  promoted  by  the  natural  tendency 
of  the  blood  to  an  alkaline  ^fpofition,  making  it 
always  approach  more  nearly  to  a putrid  acrimony, 
by  the  natural  and  neceflary  motions  of  the  heart 
and  arteries,  and  by  the  heat  which  very  much 
promotes  the  putrefadion  of  animal  humours. 
Moreover,  the  coagulable  difpofition  of  the  blood, 
continually  iofing  a great  part  of  its  water  by  in- 
fenfible  perfpiration,  requires  a fupply  of  its 
aqueous  element  to  feparaie  the  globules  and  pre- 
vent it  from  coagulation. 

ncxxxvi.  Thefe  truths  are  proved  not  only  from 
their  caufes,  but  likewife  by  the  appearances  exhibit- 
ed in  men  and  other  animals  killed  by  hunger.  For 
it  is  common  for  thefe  to  have  an  acrid  fetid  breath, 

for 


Chap.  XIX.  ^ DIGESTION.  313 

for  their  teeth  to  become  loofe  from  the  faline  acri- 
mony corroding  them,  and  to  fuffer  violent  pains 
in  the  ftomach,  acute  fever,  and  actual  madnefs. 
Thefe  diforders  are  the  more  rapid  in  their  pro- 
grefs,  the  more  violently  the  body  is  exercifed,  and 
the  more  robuft  and  younger  it  is.  They  en- 
fue  very  Ilowly  in  people  who  are  phlegmatic  and 
unaftive,  who  perfpire  little,  and  whofe  blood  cir- 
culates feebly.  Finally,  thofe  who  have  lived  with- 
out food,  have  alfo  lived  without  bodily  exercife, 
and  for  the  moft  part  laboured  under  a difeafe  of 
the  nerves. 

Dcxxxvn.  The  frefli  chyle,  compofed,  for  the 
moft  part,  of  the  acefcent  clafs  of  vegetables,  and 
always  thinner  than  the  blood,  being  received  into 
the  circulation,  tem-perates  its  putrefcent  acrimony, 
dilutes  its  impending  coagulation,  and  reduces  the 
whole  mafs  to  that  moderate  degree  of  faltnefs 
which  is  natural  to  man  : and  finally,  the  chyle, 
but  more  efpecially  that  derived  from  the  flelh  of 
animals,  and  from  the  farinaceous  grains,  furniflies 
a new  gelatinous  lymph,  which  being  applied  by 
proper  caufes  (dcccclix.)  to  the  vacuities  of  the 
wafted  folids,  repairs  that  wafte.  The  drink  di- 
lutes the  coagulable  blood,  and  hinders  its  putre- 
faction, by  feparating  its  putrefcent  particleSj 
Hence  a perfon  may  live  for  a long  time  vdthcut 
food,  if  fupplied  with  drink ; but  without  drinkj 
life  fubfifts  but  a few  days. 

Dcxxxviii.  We  are  induced  to  take  food,  both 
from  the  fenfe  of  pain  which  we  call  hunger,  and 
from  that  of  the  pleafure  imparted  by  the  fenfe  of 
tafte  (ccccLV.)  The  firft  of  thefe  proceeds  undoubt- 
edly from  the  folds  of  the  ftomach,  which  poffefs 
great  fenfibility,  being  rubbed  againft  each  other, 
by  the  periftaltic  motion,  and  by  the  prelTure  of 
the  diaphragm  and  abdominal  mufcles,  fo  that 
naked  nerves  being  rubbed  againft  naked  nerves 
excite  an  intolerabk  degree  of  pain.  Thus  man 

is 


DIGESTION. 


Chap.  XIX. 


314 

is  both  efFecluaUy  admonilhed  of  the  dangers  of 
abftinence,  and  excited  to  procure  food  by  his  la- 
bours. It  is  perhaps  increafed  by  the  gaftric  juice 
having  become  more  acrid,  unlefs  it  putrefies. 

Dcxxxix.  Thirfi;  is  feated  in  the  tongue,  fauces, 
cefoplragus,  and  ftomach.  For  whenever  thefe  parts, 
which  are  very  fenfible,  and  naturally  are  moif- 
tened  by  their  mucous  and  falival  juices,  grow 
dry  from  a deficiency  in  the  fecretion  of  thofe  hu- 
mours, or  from  muriatic  or  alkalefcent  fiilts  adher- 
ing to  them,  a much  more  intolerable  fenfation  is 
produced,  as  thirfi:  is  attended  by  much  greater 
danger,  and  does  not  abate  until  the  abundance  of 
water,  being  refiored  to  the  blood,  and  the  obfiruc- 
tion  removed  from  the  fecreting  veffels  in  the  parts 
mentioned,  they  are  again  moiftened.  From  hence 
v.'-e  learn,  why  thirfi  attends  labour,  which  exhales 
the  water  by  perfpiration  ; and  why  it  is  a fymp- 
toiTi  of  fevers,  where  the  exhaling  veffels  belong., 
ing  to  the  tongue  and  fauces  are  obfirucled  ; why 
limple  water  is  lefs  efficacious  in  allaying  thirfi  ; 
why  fubacid  liquors  are  more  efficacious,  which 
not  only  moifien  by  their  fluidity,  but  alfo,  by  a 
mild  irritation  of  the  tongue  and  mouth,  excite  a 
flow  of  the  retained  humours,  and  at  the  fame  time 
correct  putrefcency. 

DcxL.  From  thefe  caufes,  mankind  being  com- 
pelled to  take  food,  has  in  all  ages  felecfied  thefe 
fupports  of  life  from  the  vegetable  and  animal  king- 
doms, fo  that  of  the  third,  water  and  fait  alone 
are  added.  It  is  probable,  that  the  original  choice 
efi  our  foods  was  made  by  experiments,  as  fuggeft- 
ed  by  the  fmell  and  flavour  of  certain  vegetables, 
and  as  their  utility  was  confirmed  by  the  renewal 
of  flrength.  By  degrees,  as  animals  became  incom- 
modious to  hufbandmen,  and  v'egetables  alone  were 
not  fufficient  for  fupporting  them  under  their  la- 
bours, the  flefli  of  animals  was  afterwards  added. 
At  prefent,  the  number  of  •ubfiances  is  almo’l 


Chap.  XIX  DIGESTION.  315 

infinite,  which  we  take  either  as  food  or  feafon- 
ing. 

DcxLi.  Although  there  are  inftances  of  particu- 
lar perfons,  and  even  of  nations,  who  have  lived 
entirely  upon  food  taken  from  one  clafs,  as  upon 
vegetables  alone,  or  animals  alone,  and  fometimes 
upon  a few  individuals  of  one  clafs  ; and  laftly, 
upon  milk  alone  or  its  whey  ; yet  it  feems  to  be 
neceffary,  both  from  the  nature  of  the  hum.an  bod}', 
and  to  be  indifpenfable  according  to  certain  experi- 
ments, that  we  ought  to  fupport  life  efpecially  by 
two  kinds  of  food,  fo  intermixed,  that  neither  may 
exceed  ; which  mediocrity  we  are  taught  from  the 
loathing  itfelf,  which  is  excited  by  any  one  kind 
of  food  that  has  been  continued  too  long. 

DcxLii.  The  flelh  of  animals  appears  neceffary, 
from  the  teeth  in  both  jaws,  and  from  the  fabric 
of  the  human  ftomach  itfelf  refembling  that  of  car- 
nivorous animals  ; from  the  fmallnefs  and  fhortnefs 
of  the  inteftinum  caecum,  and  from  the  ftrength 
which  w'e  require.  For  the  flefli  of  animals  alone 
contains  the  gelatinous  lymph  ready  prepared, 
which,  being  extradled  from  the  broken  veffels, 
pafles  eafily  and  in  great  abundance  into  the  blood. 
Abftinence  from  animal  food  caufes  gfeat  weakneis 
both  in  the  body  and  ftomach,  and  is  ufually  at- 
tended by  a troublefome  diarrhoea.  Man  agrees 
with  the  herbivorous  animals  in  the  fize  and  length 
of  the  large  inteftines. 

DcxLiii.  Efculent  vegetables  are  generally  of  the 
acefcent  kind ; a few  of  them  only  are  either  alka- 
lefcent  or  aromatic.  Few  of  them  have  that  gluten 
which  is  fpontaneoufly  changeable  into  blood,  and 
they  only  nourifh  by  means  of  their  farina,  a fmall 
part  of  which,  after  repeated  circulations,  is  at  laft 
con-^terted  into  the  natural  juices.  Yet  they  are  ne- 
cefl'ary  to  avoid  over  repletion  with  blood,  and  of 
too  putrefcent  a kind,  from  the  ufe  of  animal  food 
alone,  fuch  as  moft  certainly  occurs  in  the  anthro- 
pophagi. 


DIGESTION. 


Chap.  XIX. 


pophagi,  and  produces  fcurvy,  ferocity,  fetor,  lep- 
rofy,  and  every  kind  of  alkaline  corruption,  all 
which  evils  are  cured  by  change  of  diet,  and  the 
excluhve  ufe  of  acid  vegetables.  Hence  we  are 
furnilhed  with  few. canine  teeth  ; and  our  appetite 
in  health,  but  more  efpecially  in  difeale,  is  ftronger 
for  acidulous  vegetables,  in  proportion  to  the 
warmth  of  our  temperament,  of  the  feafon  of  the 
year,  and  of  the  country.  Hence,  in  the  hotteft 
climates,  people  Live  almoft  altogether  upon  vege- 
tables, and  ufe  flefh  very  rarely,  and  with  danger  ; 
while,  in  the  colder  countries,  it  is  eaten  freely 
with  lefs  danger.  Hence  bread,  or  a farinaceous 
aliment  fimilar  to  it,  is  eaten  in  every  part  of  the 
world. 

DCXLiv.  The  beft  drink  is  pure  water,  free  from 
every  kind  of  fait,  and  not  impregnated  with  air, 
which  excites,  fermentations.  That  from  a moun- 
tainous fpring,  which  runs  through  a fandy  bed, 
and  is  cold,  clear,  light,  and  iniipid,  is  juftly  pre- 
ferred, Whenever  there  is  a deficiency  of  pure 
water,  as  is  frequently  the  cafe  in  fiat  countries,  or 
when  any  power  ftimulating  the  ftom.ach  to  con- 
traction, or  any  aromatic  is  required,  it  is  fupplied 
by  vinous  liquors,  efpecially  thofe  prepared  from 
grapes,  but  alfo  from  apples  and  pears  ; which,  af. 
ter  fermentation,  become  clear,  and  contain  alco- 
hol and  an  acid  fait  diluted  with  water.  Liquors 
of  the  fame  kind,  not  deftitute  of  alcohol,  but  more 
flatulent,  vapid  and  colder,  are  prepared  by  fermen- 
tation from  grain  toafled,  and  boiled  in  water,  in 
thofe  countries  where  the  grape  does  not  ripen. 

DCXLv.  Men  have  invented  various  condiments. 
They  have  added  fait,  vinegar,  and  acids  of  various 
kinds,  to  correcL  the  putrefcence  of  flefh  ; pepper, 
hot  fpices,  and  alliaceous  fubftances,  to  ftrengthen 
the  ftomach,  which  is  weakend  by  die  conflant 
ufe  of  vegetables  ; and  fugar,  lalt  and  aromatics, 
for  the  fake  of  flavouring  or  preferring  our  food. 


Chap.  XIX. 


DIGESnON. 


3^7 

But  none  of  thefe  nourifh,  being  deftitute  of  gela- 
tinous lymph,  and  nourilhing  farina.  The  fpirits 
of  wine  and  of  corn  may  be  of  fome  ufe  as  medi- 
cines, but  are  unfit  for  drinking. 

DcxLvi.  According  to  the  difference  of  country, 
climate,  or  feafon,  the  aliments  undergo  various 
preparations,  by  which  crudity  is  removed,  folid 
fibres  foftened,  exceflive  air  expelled,  difagfeeable 
acrimony  diminiflied,  or  a pleafant  flavour  impart- 
ed. But  many  vegetable  foods,  and  more  efpecial- 
ly  flefh  meats,  require  fome  trituration,  particular- 
ly in  man,  whofe  flomach  is  but  little  flefhy,  nor 
ought  the  articles  of  food  to  become  putrid  by  re- 
maining too  long  in  the  flomach. 

DcxLvii.  The  meafure  of  our  food  is  determined 
by  the  ceafing  of  our  hungei*,  which  is  different  ac- 
cording to  the  difference  of  aliments.  Animal  and 
farinaceous  food  nourifhes  moil  : other  aliments 
ought  to  fupply  by  their  quantity,  what  they  want 
in  powers  of  nourifhment.  In  general,  we  are 
nourifhed  bed  by  a fomewhat  fpare  diet,  unlefs  fub- 
jefted  to  much  labour. 

DcxLviii.  Into  the  flomach,  therefore,  the  ali- 
ments are  let  down,  often  almoft  crude,  and  little 
chewed ; of  various  kinds,  as  alkalefcent  flefh,  ran- 
cefcent  fat,  or  acefcent  vegetables,  bread  and  milk, 
and  glutinous  fubflances.  Here  they  are  digefled 
in  an  heat  equal  to  that  of  incubation,  imparted  by 
the  contiguous  heart,  liver,  and  fpleen  ; and  in  a 
cavity  fhut  above  (dcxxi.)  and  alfo  below  by  the 
afcent  of  the  pylorus,  the  narrownefs  of  the  valve 
placed  there,  and  the  a<Tion  of  the  fibres,  conflridt- 
ing  the  pylorus,  fo  that  even  milk  itfelf  remains  en- 
tirely in  thellomach  of  healthy  animals  feveral  hours 
after  meals,  without  paffmg  into  the  inteflines.  Be- 
fides,the  aliments  are  macerated  in  a moifl  place  with 
much  air,  either  fwallowed  during  deglutition,  or 
mixed  with  the  aliments.  This  air,  therefore,  ex- 
panding by  the  force  of  heat,  putrefadion,  or  fer- 
mentation. 


DIGESTION. 


Chap.  XIX. 


318 

mentation,  biirfts  the  cells  in  which  it  is  included, 
divides  the  vifcid  liquors,  weakens  the  I'olid  hbres, 
prepares  fpace  for  the  fluid  which  is  to  enter  into 
them.  But  this  air  alfo,  which  is  the  principal  ce- 
ment of  animal  folids,  emerges  from  their  fubltance, 
and  leaves  the  other  elements  without  a vinculum, 
as  we  fee  from  the  phenomena  in  Papin’s  digefter, 
in  the  ftomachs  of  animals,  and  even  in  that  of 
man.  This  air,  fet  at  liberty,  diftends  the  Itomach 
more  than  the  food  itfelf,  and  is  termed  flatus.  At 
the  fame  time,  the  aliments  begin  to  corrupt  into 
a naufeous  liquid,  often  acefcent  ; at  other  times 
putrefcent,  but  lefs  fo  in  man  from  the  influence  of 
bread  and  fait ; or  rancefcent,  as  appears  from  the 
flatus  and  eruftations,  varioufly  fetid,  and  even  in- 
flammable. This  is  the  foie  caufe  of  digeftion  in 
fifli  and  ferpents,  and  almoft  in  carnivorous  birds* 
Hence,  in  man,  metals  themfelves,  by  long  flay  in 
the  ftomach,  grow  foft,  and  are  eroded.  At  the 
fame  time  hunger  is  removed,  the  nervous  folds  of 
the  ftomach  being  removed  from  mutual  contact 
by  the  aliments  interpofed,  the  acrid  gaftric  fluid 
being  neutralized,  and  perhaps  from  the  very  pre- 
fence  of  this  naufeous  liquid  being  difagveeable  to 
the  nerves. 

ECXLix.  But  they  are  prevented  from  degener- 
ating into  complete  acidity,  by  the  heat  inducing 
putrefaction,  by  the  action  of  the  gaftric  juice,  and 
of  the  faliva,  which  is  fwallowed  to  the  amount  of 
half  an  ounce  in  an  hour,  both  inclined  to  alka- 
lefcency,  and  by  the  bile  which  certainly  regurgi- 
tates frequently  into  the  ftomach.  Thefe  fluids, 
being  incorporated  with  the  aliment,  macerate  and 
foften  it,  divide  the  membranes,  refolve  the  cellu- 
lar bands,  liquefy  the  pulps,  as  warm  water  and 
time  do  in  other  fltuations,  extract  their  juice,  and 
mingle  it  with  themfelves.  There  is,  therefore,  no 
kind  of  fermentation  in  the  ftomach,  from  whieJi 
the  nature  of  the  fluid,  and  the  defign  of  r.atur;:. 


DIGESTION. 


Chap.  XDC. 


3^9 


are  diftincl.  And  yet  the  juice  of  the  ftomach 
alone,  by  a continuance  of  its  aftion,  in  filhes,  dif- 
folves  the  bones  which  they  devour. 

DCL.  For,  the  flefhy  fibres  in  the  ftomach  being 
now  irritated  by  the  flatus,  wei^t,  and  acrimony 
of  the  food,  begin  to  contraft  themfelves  more 
powerfully  than  when  the  ftomach  is  empty,  and 
with  greater  force  in  proportion  as  it  is  more  full, 
its  round  fwelling  ftretching  the  fibres.  And,  firft, 
the  plane  of  the  fmaller  curvature  draws  the  pylo- 
rus to  the  oefephagus  ; and,  being  inferted  only  in- 
to its  left  furface,  it  draws  that  to  the  right.  The 
principal  ftratum  of  the  circular  fibres,  diminilhes 
the  cavity  of  the  ftomach,  incorporates  the  aliments 
with  the  juices,  (ncxxxiii.)  and  comprefies  them 
flightly  as  if  between  the  hands  on  oppofite  fides 
and  gradually  determines  them  towards  the  pylo- 
rus : but  it  is  not  im.mediately  permitted  to  efcape, 
both  on  account  of  the  reafon  before  afligned, 
(dcxxvi.)  and  alfo  becaufe  this  motion  begins 
from  the  part  that  is  moft  irritated  ; and,  there- 
fore, impels  the  aliment  upwards,  as  at  other  times 
it  forces  it  downwards.  The  contracted  portion  of 
the  ftomach.  propels  the  food  into  the  neighbour- 
ing dilated  part,  and  is  in  its  turn  relaxed  when 
that  other  is  contracted.  Thefe  alternate  contrac- 
tions at  laft  terminate  in  complete  evacuation.  In 
this  action,  there  is  nothing  which  refembles  the 
trituration  made  by  the  ftrong  gizzards  of  granivo- 
rous  fowls,  which  fome  anatomifts  have  afcribed  to 
the  human  ftomach  ; yet  it  has  a confiderable  de- 
gree of  ftrength,  and  afibrds  an  example  of  fibres 
contracted  to  more  than  a third  part  of  their  length; 
for  the  ftomach  is  frequently  reduced  to  much  lefs 
than  a third  of  its  diameter,  even  to  the  breadth  of  an 
inch  ; and,  laftly,  is  capable  of  difcharging  needles. 
Yet  it  neither  bruifes  berries,  nor  the  fofteft  worms. 

DC  LI.  The  action  exerted  by  the  diaphragm  and 
mufcles  of  the  abdomen,  is  ftronger  than  the  peri- 
ftaltic  force  of  the  ftomach  ; for,  by  this,  it  is  ca- 
pable 


DIGESTION. 


Chap.  XIX. 


pable  of  perfectly  evacuating  the  ftomach,  and  of 
bringing  its  anterior  and  pofterior  fides  into  actual 
contaft.  For  this  force,  principally,  expels  tlie 
fluids  immediately,  but  the  folids  only  when  they 
ave  foftened,  ancf  rendered  fmall  enough  for  the 
valve  of  the  pylorus,  through  that  pylorus  into  the 
duodenum,  which  is  inclined  when  the  ftomach  is 
full ; for  the  aliments  do  not  feem  to  leave  the 
ftomach,  before  they  have  loft  their  fibrous  or  other 
texture,  and  are  refolved  into  a mucous,  yellow- 
ifti,  cineritior^,  fomewhat  fetid,  pultaceous  liquid. 
That  which  is  firft  prepared  and  liquefied,  goes 
firft,  and,  therefore,  water  and  milk,  firft  of  all  ; 
then  pot  herbs  ; and,  laftly,  flefli.  The  harder, 
tougher,  and  longer  fkins  or  fibres,  pafs  at  the 
fame  time  unchanged  : and  fuch  things  as  are  hard 
and  too  large  to  pafs  the  pylorus,  are  retained  in 
the  ftomach  for  a long  time. 

DCLii.  But  the  moll  confidcrable  portion  of  the 
drink  is  abforbed  by  the  pendulous  patulent  veins 
of  the  ftomach  itfeif,  correfponding  to  the  exhaling 
arteries  (ccxxxiii.)  and  is  carried  by  a fhorter  way 
to  the  blood,  as  plainly  appears  from  injecUons.  Does 
any  thing  enter  the  lymphatic  veffels  (dcxxxi.)  ? 

Dcniii.  The  ftomach,  being  irritated  by  too  great 
a quantity  or  acrimony  of  the  food,  or  elfe  by  nau- 
fea  from  regurgitation  of  the  bile,  or  other  caufe, 
V/ith  an  antiperiftaltic  motion  repels  its  contents  up- 
wards, and  difcharges  them  through  the  open  and 
relaxed  cefophagus,  by  vomiting.  But  this  is  allift. 
ed  by  the  aftion  of  the  abdominal  mufcles,  which 
comprefs  the  belly,  draw  in  the  ribs,  and,  as  the 
defcending  diaphragm  a<ft;s  againft  them,  they  eva- 
cuate the  ftomach  with  very  great  force,  fqueezed 
as  if  in  a prefs. 

DCLiv.  But  the  aliments  tranfmitted  in  their  na- 
tural ccurfe  to  the  duodenum,  meet  there  with  the 
bile  which  frequently  regurgitates  into  the  ftomach 
itfeif,  and  with  the  pancreatic  juice.  The  nature 

of 


Chap.  XX,  OMENTUM.  32  x 

of  the  former  of  thefe,  the  principal  fluid  of  cligeE 
tion,  requires  a previous  hiftory  of  the  vifcera^ 
^'hieh  tranfmit  their  blood  to  the  vena  portarum,' 


C H A P.  XX. 

THE  OMENTUM. 

bcLV,  "'HE  perltonteum  is  a ftrorig  hmpie  mem- 
i brane,  by  which  all  the  vifeera  of  the 
abdomen  are  furronnded.  It  has  an  exceedingly 
fmooth,  exhaling,  and  moifl  internal  furface  5 out- 
wardly, it  is  every  where  furrounded  by  cellular 
fubftance  ; which,  towards  the  kidneys,  is  very 
loofe  and  very  fat ; but  is  extremely  fliort  at  the 
lower  tendon  of  the  tranfverfe  mufcles*  It  begins 
from  the  diaphragm,  which  it  completely  lines  ; 
and  at  the  laft  flelhy  fibre's  of  the  ribs,  and  the  ex- 
ternal lumbar  fibres,  it  completes  the  feptum,  in 
eonjunftion  with  the  pleura,  Vvuth  which  it  is  con- 
tinuous through  the  various  intervals  of  the  dia- 
phragm, It  defcehds  behind,  before  the  kidneys  ; 
before,  behind  the  abdominal  mufcles  ; it  dips  into 
the  pelvis  ; from  the  bones  of  the  pubes,  pafies  over 
the  bladder,  and  defcends  behind  it ; and  being 
again  carried  backwards  at  the  entrance  of  the  ure- 
ters in  two  lunar  folds,  it  rejoins  upon  the  intefli- 
num  rectum,  that  part  of  itfelf  which  invefts  the 
loins,  and  in  this  fituation  lies-  before  the  reftum. 

DCLvi.  The  cellular  texture,  which  covers  the 
peritonaeum  on  the  outfide,  is  continued  into  fheaths 
in  very  many  places  ; of  which  one  receives  the  tef- 
ticle,  on  each  fide  ; another  the  iliac  veffels  j others 
the  inteftinUm  reftum,  the  large  veffels  of  the  pel- 
vis, the  obturatoria,  penis,  bladder,  and  aorta,  and 
afcending,  into  the  breaft,  accompany  the  gullet  and 
vertebr;s  j by  means  of  which,  there  is  a commu- 
X nication 


322  OMENTUM.  Chap.  XX. 

nicatlon  between  the  whole  body  and  the  peritonaea 
um,  well  known  in  dropfical  people. 

DCLvii.  It  has  various  prolongations  for  covers 
ing  the  vifeera.  The  fliorter  productions  of  this 
membrane  are  called  ligaments  ; and  are  formed  by 
a continuous  reduplication  of  the  peritonaeum,  re- 
ceding from  its  inner  furface,  inclofmg  cellular  fub- 
ilancc,  and  extending  to  fome  vifeus,  where  its 
plates  feparate  ; and  having  diverged,  emibrace  the 
vifeus  ; but  the  intermediate  cellular  lubftance  al- 
ways accoiripanies  this  membranous  coat,  and  joins 
it  with  the  true  fubftance  of  the  vifeus.  Of  this 
Utort  kind  of  production,  three  belong  to  the  liver, 
one  or  two  to  the  fpleen,  and  others  tothelddneys 
and  to  the  fides  of  the  uterus  and  vagina.  By  this 
means,  the  tender  fubftance  of  the  vifeera  is  defend- 
ed from  injury  by  any  motion  or  concuilion,  and 
their  whole  mafs  is  prevented  from  being  mifplaccd 
by  their  own  weight,  and  from  injuring  themfelves, 
being  fecurely  connected  with  the  firm  fides  of  the 
peritonaeum. 

DCLviii.  But  the  moft  important  of  all  thefe 
productions  of  the  peritonaeum,  are  thofe  called  the 
mefentery  and  mefocolon  ; and  the  defeription  of 
which,  although  very  difficult,  ought  not  to  be  fe- 
parated.  We  fliall,  therefore,  begin  firfl;  with  the 
mefocolon,  as  being  the  moft  fimple.  In  the  pel- 
vis, the  peritonasum  fpreads  itfelf  Ihortly  before  the 
reftura.  But  where  that  inteftinc  becomes  loofe, 
and  forms  the  femilunar  curve,  the  peritonxum 
there  rifes  confiderably  from  the  middle  iliac  vef- 
fels  and  region  of  the  pfoas-  mufcle,  double  (dclvii.) 
and  with  a figure  adapted  for  receiving  the  hol- 
low colon.  But  above,  on  the  left  fide,  the  co- 
lon is  connected  with  almoit  no  intermediate 
loofe  production  to  the  peritonxum,  fpread  upon 
the  pfoas  mufcle,  as  high  as  the  fpleen,  where  this 
part  of  the  peritonxum,  which  gave  a coat  to  the 
colon,  being  extended  under  the  fpleen,.  receive* 


Chap.  XX.  OMENTUM.  3-3 

and  fuftains  that  vifcusj  in  a hollow  fiiperior  re- 
cefs. 

DCLix.  Afterwards  the  peritonaeum,  from  the 
left  kidney,  from  the  interval  between  the  kidneys, 
from  the  large  veffels,  and  from  the  right  kidney, 
emerges  forwards,  under  the  pancreas  ; and  forms 
the  broad  and  fufficiently  long  continuous  produc- 
tion, called  the  tranfverfe  mefocolon,  which,  like  a 
partition,  divides  the  upper  part  of  the  abdomen, 
containing  the  ftomach,  liver,  fpleen,  and  pancreas, 
from  the  lower  part.  The  lower  plate  of  this  tranf- 
verfe production,  is  continued  hngly  from  the  right 
mefocolon  to  the  left,  and  ferves  as  an  external  coat 
1,0  a pretty  large  portion  of  the  lower  and  defcend^- 
ing  part  of  the  duodenum;  But  the  upper  plate, 
lefs  hmple  in  its  courfe,  departs  from  the  lumbar 
peritoneum  at  the  kidney  and  -region  of  the  vena 
cava,  farther  to  the  right  than  the  duodenum,  to 
which  it  gives  an  external  membrane,  not  quite  to 
the  valve  of  the  pylorus  ; and,  beyond  this  intef- 
tine,  and  beyond  the  colon,  it  is  joined  with  the 
lower  plate,  fo  that  a large  part  of  the  duodenum 
lies  within  the  cavity  of  the  mefocolon.  After- 
wards, in  the  region  of  the  liver,  the  mefocolon  is 
infleCfed,  and  defeending  over  the  kidney  of  the 
fame  hde,  much  fhorter,  it  includes  the  right  of  the 
colon,  as  far  as  the  inteftinum  caecum,  which  refts 
upon  the  iliac  mufcle,  and  the  appendix,  which  is 
provided  with  a peculiar,  long,  curved  mefentery. 
There  the  mefocolon  terminates,  almoft  at  the  bi- 
furcation of  the  aorta. 

DC  LX.  The  whole  of  the  mefocolon,  and  of  the 
mefentery,  is  hollow ; fo  that  air  may  be  forced  in 
between  its  two  limilar  plates,  in  fuch  a manner  as 
to  expand  it  into  a bag;  At  the  place  where  it  fuf- 
tains the  colon,  and  alfo  from  part  of  the  intelUnum 
rectum,  the  mefocolon,  continuous  with  the  outer 
membrane  of  the  intclline,  forms  itfelf  into  fmall 
flender  bags,  refembling  the  omentum,  for  the  moft 
x 2 part 


OMENTUM. 


Chap.  XN.- 


P'4 

part  in  pairs,  with  their  loofe  extremities  thicker 
and  bifid,  and  capable  of  admitting  air,  blown  in 
between  the  plates  of  the  mefocolon. 

Dci.xi.  In  the  next  place,  vv*e  come  to  the  me- 
fentery,  a very  large,  folded  production  of  the  pe- 
ritonaeum, continuous  with  the  tranfverfe  and  right 
mefocolon,  at  the  right  fide  of  the  emerging  duo- 
denum ; and  then  proceeding  for  a long  way  vath 
both  mefocolons,  even  as  low  as  the  pelvis.  The 
mefentery,  under  the  right' portion  of  the  tranfverfe 
mefocolon,  defeending  from  that  part  of  the  perito- 
naeum, which  lies  upon  the  aorta,  under  the  pan- 
creas, and  having  numberlefs  folds  in  its  edge,  con- 
tains the  very  long  feries  of  the  fmall  inteftines. 

DCLxii.  Every  part  of  the  mefentery  and  mefo- 
colon contains  fat,  collected  in  the  neceilary  inter- 
val of  the  plates  ; generally  in  greater  quantit)', 
where  they  are  loirger  ; and  interpofed  vefl'els  dif- 
tributed  around  the  fat,  which  the  arteries  fccrete, 
•and  the  veins,  as  already  mentioned,  abford ; and 
ahb  very  numerous  glands,,  which  are  moft  confpi- 
cuous  in  a young  fubjeef. 

Dcnxim  The  nature  of  the  omentum  is  very 
analogous  to  that  of  the  mefenteiy.  But  there  arc 
many  membranes  that  come  under  this  general  de- 
nomination, of  the  fame  ftructure  and  utility,  all 
eompofed  of  a tender  membrane,  very  eafily  lace- 
rated, through  which  reticulated  velTels  are  dif- 
tributed,  with  fat  depofited  in  ftreaks  along  their 
courfe.  This  membrane  is  always  double ; and  be- 
tween its  lamellee,  clofely  connecled  by  very  ten- 
der cellular  fubftance,  the  veflels  are  diftributed, 
and  the  fat  collected.  And,  firll,  where  the  top  of 
the  right  kidney,  and  the  lobulus  caudatus  of  the 
liver,  with  the  fubjacent  large  veflels,  form  an  an- 
gle with  the  duodenum,  there  the  external  mem- 
brane of  the  colon  which  comes  from  the  peritn- 
nasum,  joining  with  the  membrane  of  the  duode- 
num, which  alfo  avifes  immediately  from  the  perk 

tona^um. 


Chap.  XX. 


OMENTUM. 


325 

tonasum  lying  upon  the  kidney,  enters  backwards 
into  the  tranfverfe  fiffure  of  the  liver  for  a confid- 
erable  fpace,  is  continuous  vath  its  external  coat, 
contains  the  gall  bladder,  fupports  the  hepatic  vef- 
feis,  and  is  very  yellow  and  llippery.  Behind  this 
membranous  production,  betwixt  the  right  lobe  of 
the  liver,  hepatic  veffels,  vena  portarum,  biliary 
ducts,  aorta,  and  adjacent  duodenum,  there  is  a nat- 
ural opening,  by  which  air  may  be  blown  extenlively 
into  all  that  cavity  of  the  omentum,  which  we  fliall 
prefently  defcribe  ; and,  laftly,  into  the  bags  of  the 
reft  of  the  omentum. 

DCLXiv.  From  thence,  in  a courfe  continuous 
with  this  membrane  (dclkiii.)  from  the  pylorus  and 
the  fmaller  curvature  of  the  ftomach,  the  external 
membrane  of  the  liver  joins  in  fueh  a manner  with 
that  of  the  ftomach,  that  the  thin  membrane  of  the 
liver  is  continued  out  of  the  folTa  of  the  venal  duft, 
acrofs  the  little  lobe,  into  the  ftomach,  ftretched 
before  the  lobe  and  before  the  pancreas.  This  is  the 
little  omentum  or  hepatieo  gaftricum  ; which,  when 
inflated,  refembles  a cone  ; and  gradually  becoming 
harder,  and  emaciated,  it  changes  into  a true  liga- 
ment, by  which  the  oefophagus  is  connecled  to  the 
diaphragm  (dcxxiii.) 

DCLXv.  But  the  larger  omentum,  the  gaftrocoll- 
cum,  is  of  a much  greater  extent.  It  begins  at  the 
flrft  aceeflion  of  the  right  gaftro-epiploic  artery  to 
the  ftom.ach,  being  continued  there  from  the  upper 
plate  of  the  tranfverfe  mefocolon  (dclix.)  ; and 
then  from  the  whole  great  curve  of  the  ftomach, 
as  far  as  the  fpleen,  and  alfo  from  the  right  convex 
end  of  the  ftomach  towards  the  fpleen,  until  it  alfo 
terminates  in  a ligament  that  ties  the  upper  and 
back  part  of  the  fpleen  to  the  ftomach.  This  is  the 
anterior  lamina. 

DCLXvi.  Being  continued  downwards,  fometimes 
to  the  navel,  fometimes  to  the  pelvis,  it  hangs  be- 
fore the  inteftines,  and  behind  the  inufdes  of  the 

abdomen, 


OMENTUM. 


Chap.  XX. 


326 

abdomen,  until,  from  its  lower  edge  being  reflected 
upon  itfelf,  it  afcends,  leaving  an  intermediate  va- 
cuity between  it  and  the  anterior  lamdna,  and  is 
continued  for  a very  great  extent  into  the  external 
membrane  of  the  tranfverfe  colon,  and  laftly  into 
the  Jlnus  of  the  ipleen,  by  which  the  large  blood- 
vefl’els  are  received,  and  it  ends  finally  on  the  oefo- 
phagus,  under  the  diaphragm.  Behind  the  ftomach, 
and  before  the  pancreas,  its  cavity  is  continuous 
with  that  of  the  fmaller  omentum. 

DCLxvii.  To  this  the  om.entum  colicum  is  con- 
nected, which  arifcs  farther  to  the  right  than  the 
firft  origin  of  the  omentum  gaftrocolicum  from  the 
meibcolon,  with  the  cavity  of  which  it  is  contin- 
uous, but  produced  folely  from  tlie  colon  and  its 
external  membrane,  which  departs  double  from  the 
intcfline  ; it  is  prolonged,  and  terminates  by  a co- 
nical extremity,  fometimes  of  longer,  fometimes  of 
fliorter  extent,  above  the  inteflinum  cxcum. 

DCLXviii.  The  ufes  of  the  omentum  are  many. 
In  common  with  the  mefentery,  it  forms  loofe  fpa- 
ces,  into  ayhich  the  fat  may  be  poured,  and  pre- 
ferved  during  fleep  and  inactivity,  that  it  may  be 
afterwards  diiTolved  by  increaie  of  motion,  reftored 
by  the  abforbent  veins,  and  conftitute  a principal 
ingredient  of  the  bile.  Hence  it  is  fometimes  found 
very  thick,  even  an  inch  thick,  and  at  others  thin, 
and  more  tranfparent  than  paper.  For  that  the  fat 
returns  ao-ain  into  the  veins,  is  demonftratcd  from 
human  omenta  being  found  of  very  difierent  bulks 
and  fatnefs,  according  as  they  belonged  to  indolent, 
laborious,  or  difeafed  fubjects  ; from  the  phenomena 
in  animals  ; from  the  analogy  of  all  the  reft  of  the 
fat  of  the  human  body  (xx.)  ; from  experiments  in 
frogs,  where  this  reabforption  of  the  fat  may  be 
made  evident  to  the  eye  ; and,  laftly,  from  the  evi- 
dently inflammable  nature  of  the  bile.  Hither  I 
alto  refer  the  diforders  of  digcftion,  the  crudities 


Chap.  XX.  OMENTUM.  327 

and  coldnefs  of  the  ftomach,  obferved  from  cutting 
out  the  omentum. 

DCLXix.  For  all  the  blood  which  returns  from 
the  omentum  and  mefocolon,  goes  into  the  vena 
portarum,  and  by  that  into  the  liver  itfelf.  The 
omentum  gaftrocolieum  is  furnifhed  with  blood 
from  each  of  the  gaftro-epiploic  arteries,  by  many 
defcending  reticulated  branches  : of  which  the  moft 
lateral  are  the  longeft,  and  the  loweft  anaftomofe 
by  minute  twigs  with  thofe  of  the  colon.  It  alfo 
has  branches  from  the  fplenic,  duodenal,  and  adi- 
pofe  arteries.  The  omentum  colicum  has  its  arte^ 
ries  from  the  colon,  as  alfo  the  fmaller  appendices, 
(dclx.)  and  from  the  duodenal  and  right  epiploic, 
'fhe  arteries  of  the  fmaller  omentum  come  from  the 
hepatics,  and  from  the  right  and  left  coronaries. 

Dci.xx.  The  omentum,  being  fat  and  indolent, 
has  very  fmall  nerves.  They  arife  from  the  nerves 
of  the  eighth  pair,  both  in  the  greater  and  in  the 
leffer  curvatures  of  the  ftomach. 

DCLXxi.  The  arteries  of  the  mefentery  are,  in 
general,  the  fame  with  thofe  which  go  to  the  in-^ 
teftines,  and  of  which  the  fmaller  branches  remain 
in  the  glands  and  fat  of  the  mefentery.  Various 
fmall  acceflbry  arteries  go  to  both  mefocolons,  from 
the  intercoftals,  fpermatics,  lumbars  and  capfulary,  to 
the  tranfverfe  portion,  from  the  fplenic  artery  and 
pancreatico  duodenalis,  and  to  the  left  mefocolon, 
from  the  branches  of  the  aorta  going  to  the  lumbar 
glands. 

DCLxxii.  The  veins  of  the  omentum,  in  general, 
accompany  the  arteries,  and  unite  into  ftmilar 
trunks  : thofe  of  the  left  part  of  the  gaftrocolic 
omentum  into  the  fplenic,  and  alfo  thofe  of  the  he- 
paticogaftric,  which  likewife  fends  its  blood  to  the 
trunk  of  the  vena  portarum  : thofe  from  the  larger 
and  right- part  of  the  gaftrocolic  omentum,  from  the 
omentum  colicum,  and  from  the  appendices  epiplo^ 
ides,  into  the  mefenteric  trunk.  All  the  veins  of  the 

mefenterv 


OMENTUM. 


Chap.  XX. 


528 

mefentery  meet  together  in  one,  which  is  the  true 
trunk  of  the  vena  portarum  : being  collected  firft 
into  two  large  branches  ; of  which  the  one,  the  me- 
lenteric,  receives  the  gaftro-epiploic  vein,  the  colicse 
mediae,  the  iliocolica,  and  all  thofe  of  the  fmall  in- 
teftines  as  far  as  the  duodenum  ; the  other,  which 
going  tranfverfely  inferts  itfelf  into  the  former, 
above  the  origin  of  the  duodenum,  carries  back  the 
blood  of  the  left  colic  veins,  and  thofe  of  the  rec- 
tum, except  the  lowermoft,  which  belong  partly  to 
thofe  of  the  bladder,  and  partly  to  the  hypogaftric 
branches  of  the  pelvis.  The  vein  which  is  called 
haemorrhoidalis  interna,  is  fometimes  inferted  rath- 
er into  the  fplenic  than  into  the  mefenteric  vein. 
Idas  the  omentum  alfo  lymphatic  vefiels  ? Certain- 
ly  there  are  conglobate  glands,  both  in  the  little 
omentum  and  in  the  gaftrocolicum  ; and  ancient 
anatomifts  have  obfeiu'ed  pellucid  velfels  in  the 
omentum  ; and  a modern  has  defcribed  them  for 
lacleals  of  the  flomach. 

DCLXxiii.  The  other  ufes  of  the  omentum  are,  to 
interpofe  itfelf  betwixt  the  inteftines  and  perito- 
naeum, which  are  very  apt  to  adhere  ; to  preferve 
the  mobility  of  the  former  entire,both  among  them- 
fclves  and  upon  tlie  peritonaeum  ; to  lelfen  friction  ; 
and  to  lubrica.te  the  mufcular  fibres  with  a very  bland 
oil.  Therefore,  even  in  infects,  there  is  a great 
deal  of  fat  around  the  inteftines.  In  the  large  in- 
teftincs,  there  are  a great  many  appendices,  becaufe 
they  have  larger  lacerti,  and  cannot  be  altogether 
covered  by  the  omentum'.  The  omentum  aUb  ar- 
ranges the  vefiels,  conducts  and  fupports  them,  con- 
necls  the  contiguous  vifcera,  and  exhales  a foft  va- 
pour, which,  mixing  with  watery  abdominal  exha- 
lations, anoints  and  lubricates  all  the  vifcera. 

DC  I, XXIV.  The  mefentery  fuftains  the  inteftines 
in  fuch  a manner,  that  they  poflefs  both  mobility 
and  firmnefs  : it  fupports  and  conduces  with  fafety 
the  blood-veffels,  ladeals  and  nerves  3 it  fixes  tlie 

eland'-- 


SPLEEN. 


Chap.  XXL 


329 


glands,  as  ftiall  be  noticed  hereafter,  gives  an  exter- 
nal coat  to  the  inteftines,  and  forms  moft  of  the 
omenta. 

D c L X X V.  But  befides , theblood,  returning  through 
the  mefenteric  and  mefocolic  veins,  brings  with  it 
to  the  liver  a fecond  principal  conftituent  of  the 
bile  ; namely,  a copious  fubalkaline  humour,  which 
is  abforbed  from  all  the  fmall  inteftines,  as  will  be 
demonftrated  in  its  proper  place.  Moreover,  from 
the  large  inteftines,  it  conveys  to  the  liver  another 
fluid,  but  more  putrid,  fetid,  and  nearly  approach- 
ing to  the  nature  of  volatile  alkali,  abforbed  from 
the  alvine  faeces,  that  now  begin  to  fmell  ftrong  ; 
which  is  eaftly  proved,  both  from  proper  experi- 
ments,and  from  the  induration  of  the  faeces  when  too 
long  retained  in  the  bowels.  For  this  water  is  nat- 
urally fluid,  and  rendered  more  fo  by  incipient  pu- 
trefaction ; it  moderates  the  tenacity  of  the  oil  from 
the  omentum  and  mefentery,  and  keeps  it  from  co- 
agulation. But  it  efpecially  imparts  to  the  bile  that 
alkaline  rancidity  with  which  it  abounds,  and  on 
which  the  great  tenuity,  and  dyeing  and  fapona- 
ceous  powers  of  the  bile  almoft  folely  depend. 


DCLXXvi,  HE  fpleen  is  alfo  one  of  thofe  vifcera. 


It  is  pulpy,  bloody,  livid,  and  fomewhat  thick ; of 
an  oval  circumference,  often  notched  on  the  mar- 
gin, or  even  divided  into  lobes  ; on  one  fide,  to- 
wards the  ribs,  convex,  on  the  other  concave ; with 
two  furfaces,  one  anterior  towards  the  ftomach,  and 
another  pofterior  towards  the  diaphragm  ; divided 
by  the  entrance  of  its  veflels ; and  with  two  extrem- 
Uie;3,  of  which  the  inferior  and  anterior  is  the 


CHAP,  XXL 


SPLEEN, 


which  fend  their  blood  to  the  liver. 


lharpeft. 


SPLEEN. 


Chap.  XaI, 


S3® 

fharpeft.  It  is  connected  to  the  ftomach  by  the 
little  omentum  and  upper  ligament,  fupported  from 
the  adjacent  colon  by  the  ligament  (dclviii.)  be- 
hind, it  is  contiguous  to  the  renal  capfule  ; and  it 
is  connected  to  the  kidney  by  the  peritonaeum.  It 
alfo  receives  the  peritonaeum  from  the  diaphragm, 
under  the  denomination  of  a ligament,  in  the  back 
part  of  its  hollow  hnus,  behind  its  veffels.  Its  fit- 
uation  is  variable,  and  depends  on  the  ftomach. 
When  that  is  empty,  the  fpleen  is  placed  more 
perpendicularly,  and  its  extremities  become  fu- 
perior  and  inferior  ; but  when  the  ftomach  is  full, 
and  its  middle  curv'ature  arifes  forwards  (dcxxii.) 
then  the  fpleen  at  the  fame  time  changes  its  fit- 
uation,  and  its  extremities  become  anterior  and 
pofterior,  fo  as  to  lie  almoft  tranfverfely.  Alfo, 
being  of  a very  foft  texture,  it  is  more  fpongy 
and  larger  when  the  ftomach  is  empty  ; and  when 
the  ftomach  is  full,  being  prefled  by  it  againft  the 
ribs,  it  is  emptied.  Hence,  in  weak  fubjecfts,  it  is 
large ; but  in  thofe  who  die  fuddenly,  and  in  full 
health,  it  is  fmall.  It  alfo  defccnds  with  the  dia- 
phragm in  inipiraticn,  and  afcends  with  it  in  exfjft- 
ration  ; and  befldes,  it  frequently  varies  its  fltua- 
tion  with  the  colon.  Frequently  there  is  a fecond 
acceffory  fpleen,  or  even  fcveral. 

DCLXxvii.  The  blood -veflels  of  the  fpleen  are 
large,  in  proportion  to  its  weight.  The  arterial 
trunk  comes  from  the  cceliac  ; the  left  branch  of 
which  proceeds  in  a Terpentine  courfc,  above  and 
behind  the  pancreas,  to  which  it  gives  branches, 
and  to  the  inefocolon,  ftomach,  and  omentum,  iur 
curvated  along  the  fulcus  of  the  fpleen,  and  being 
fupported  by  the  right  end  of  the  gaftrocolic  omen- 
tum, it  in  a manner  perforates  the  fpleen  by  many 
branches.  The  thicknefs  of  this  artery  is  greater 
than  that  of  the  aorta.  The  fplenic  vein  is  remark- 
ably foft,  almoft  more  fo  than  any  other  vein  ot  the 
body  j it  forms  the  principal  kft  branch  of  the  vena 

portarum. 


SPLEEN. 


Chap.  XXL 


331 


portarum,  and,  befides  the  branches  accompanying 
the  arteries,  it  receives  the  great  coronary,  defcend- 
ing  behind  the  pancreas,  and  fometimes  the  internal 
hsemorrhoidal.  The  vafa  brevia,  arifing  from  thofe 
of  the  fpleen,  we  have  mentioned  elfewhere  ; and 
laftly,  fmall  twigs  from  the  lumbars,  phrenics,  in- 
tercoftals,  and  thofe  of  th^  renal  capfules,  go  to  tho 
ligaments  and  membranes.  In  like  manner,  the 
fplenic  and  fliort  veins  communicate  with  the  renal 
capfulary,  renal  and  phrenics. 

DCLXxviii.  The  lymphatic  velTels  which  are  de- 
fcribed  in  the  duplicature  of  the  membrane  of  the 
fpleen,  which,  however,  does  not  exift,  and  are  faid 
to  proceed  on  to  the  receptacle  of  the  chyle,  are 
very  evident  in  the  calf;  and  in  mankind  are  ren- 
dered confpicuous  by  blowing  air  under  the  mem- 
brane, or  by  maceration,  or  by  injecHng  water  in- 
to the  artery. 

DCLxxix.  The  nerves  of  the  fpleen  are  fmall ; fo 
that  it  is  little  fufceptible  of  pain,  and  is  very  rarely 
inflamed.  They  arife  from  a particular  plexus  of 
the  pofterior  branches  of  the  eighth  pair,  (dcxxX.) 
and  of  peculiar  branches  from  the  large  gangliform 
plexus,  which  the  fplenic  trunk  of  the  intercoftal 
nerve  produces  ; and  they  furround  the  fplenic  ar- 
tery with  branches. 

DCLxxx.  The  fabric  of  the  fpleen  appears  to  be 
much  more  fimple  than  is  commonly  believed.  For 
it  is  compofed,  both  in  man  and  in  calves,  entirely 
of  arteries  and  of  veins  ; the  former  of  which  are 
remarkably  branchy,  and  fubdivided  into  fewer 
large  branches,  but  into  very  numerous  minute 
ones,  terminating  finally  in  very  tender  twigs,  very 
difficult  of  injedlion,  and  arifing  very  crowded  to- 
gether ; from  which  there  is  a ready  paffage  into 
the  correfponding  veins.  Various  authors  have 
confidered  thefe  pencils,  with  their  parallel  branch- 
es, being  fomewhat  round,  as  glands.  Injeftion, 
rightly  managed,  never  efcapes  into  any  intervals  ; 

noy 


SPLEEN. 


Chap.  XXI. 


332 

nor  have  hollow  glands  ever  been  demonftrated 
with  certainty.  Each  little  arterial  trunk,  with  the 
fmaller  t wigs  that  proceed  from  it,  is  furrounded 
by  a very  fine  cellular  web,  in  the  fame  manner  as 
in  all  the  vifcera,  but  here  rather  fofter.  The 
whole  body  of  the  fpleen  is  externally  furrounded 
by  a lingle  membrane,  hmple  and  not  very  firm, 
continued  from  the  peritonaeum,  and  joined  to  the 
fubftance  of  the  fpleen  by  thicker  cellular  fub- 
flance. 

DCLXxxi.  Obfervation  alfo  teaches  us,  that  the 
fpleen  contains  more  blood,  in  proportion,  than  any 
other  vifcus  •,  lince  it  has  no  mufcles,  fat,  air  veffels, 
or  excretory  duels,  interpofed  between  its  blood- 
vellels.  Its  blood  is  fcarcely  ever  coagulated,  has 
a fomewhat  dark  colour,  and  from  its  dilution,  col- 
our, and  greater  proportion  of  water,  ma)  be  al- 
moll  compared  to  the  foetal  blood.  It  abounds  with 
water  and  volatile  fait’,  but  has  lefs  oil. 

DCLXxxii.  The  want  of  an  excretory  duel  to  the 
fpleen,  has  occafioned,  in  all  ages,  inquiries,  doubts, 
and  controverfies,  about  its  ufe.  The  following 
feems  to  us  to  correfpond  with  its  fabric ; al- 
though, perhaps,  all  the  ufes  of  the  fpleen  are  not 
comprehended  by  it.  A great  quantity  of  blood  is 
carried  to  the  fpleen,  (dclxxvii.)  and,  from  the 
denfity  and  ferpentine  courfe  of  the  artery,  its  mo- 
tion is  flow ; but,  when  the  flomach  is  empty,  at 
which  time  it  arrives  in  greater  quantity,  ar.d  being 
lefs  compreffed,  is  retained  in  the  fpleen,  it  in  fome 
meafure  ftagnates,  from  the  very  great  proportion 
of  branches  to  the  trunks  in  this  part ; and  the  dif- 
hcult  circulation  of  the  blood  of  the  fpleen  through 
the  llraits  of  the  liver.  Hence  the  very  frequent 
fchirrofities  of  the  fpleen  ; hence  that  immenfc 
quaiitity  of  blood  with  which  the  wliole  fpleen  is 
dillended,  and  which  is  not  found  in  any  other  vil- 
cus  in  fuch  epantity.  Therefore  the  blood,  in  tins 
warm  ftuation,  and  fomented  by  the  putrid  faces 


Chap.  XXI. 


SPLEEN. 


333 


of  the  adjacent  colon,  is  refolved,  and  afterwards 
advances,  in  a certain  degree,  towards  putrefac. 
tion,  as  appears  from  its  colour  and  fluidity.  But 
it  is  the  more  fluid,  becaufe  the  fpleen  has  no  fc- 
cretory  veflels,  and  therefore  the  whole  quantity 
of  water  enters  the  vein,  which  was  brought  by  the 
artery. 

DC  LX  XXIII.  Then,  when  the  ftomach  is  filled 
with  food  or  flatus,  the  fpleen  is  comprefled  into  a 
narrower  compafs,  againll  the  reflfting  ribs  and  fu- 
perincumbent  diaphragm,  and  the  blood  which 
was  returning  through  the  fplenic  vein,  flowly  and 
in  fmall  quantity,  is  fuddenly  prefled  out  of  the 
ipleen,  returns  with  celerity  to  the  liver  ; mixes 
with  the  fluggifli  blood  loaded  with  the  fat  of  the 
omentum  and  mefentery,  (dclxix.)  dilutes  it,  pre- 
ferves  it  from  coagulation  and  ftagnation  ; and,  at 
the  fame  time,  it  conduces  to  increafe  the  fecretion' 
of  bile,  at  the  time  when  it  is  moft  wanted,  for  the 
procefs  of  digeftion  which  is  then  going  on.  The 
Ipleen,  tlierefore,  feems  to  fupply  to  the  bile  fome 
aqueous  principle,  but  probably  of  a fubalkaline  na- 
ture, and  acrid  from  its  ftagnation. 

DCLxxxiv.  Is  the  fabric  of  the  fpleen  cellular  ? 
Does  the  blood  poured  out  into  thofe  cells  ftagnate  ? 
Is  it  diluted  with  fome  juice  fecreted  by  peculiar 
glands  ? Nothing  of  this  is  demonftrated  by  anat- 
omy ; nor  do  liquids  or  wax  ever  efcape  from  the 
arteries,  unlefs  injefted  with  two  great  violence.  Is- 
an  acid  juice  prepared  in  the  fpleen  for  the  ftomach  ? 
That  opinion  is  difcarded,  as  repugnant  to  the  na- 
ture of  all  the  animal  juices,  and  inadmiflible,  from 
the  want  of  a paflage.  Is  the  fpleen  ufelefs  ? Is  this 
proved,  by  the  little  injury  animals  fuftain  from  its- 
extirpation  ? The  lofs  even  of  a confiderable  part  does 
not  injure  a robuft  animal ; and  yet  there  are  exam- 
ples, where,  from  its  extirpation,  the  liver  became 
fwelled  and  difeafed,the  bile  more  fcanty  and  darker,-^ 
and  troublefome  flatulencies  fucceeded,  which  are  re- 
ferable' 


PAITCREAS. 


Chap.  XAH; 


ferable  to  the  vitiated  nature  of  the  bile,  the  ob- 
ftruflion  of  the  liver,  and  diminillied  powers  of  di- 
geifion  ; if  they  were  confirmed  by  repeated  ex- 
periments. 


CHAP.  xxn. 

PANCREAS. 

DCLXXXv.  pancreatic  juice,  which  is  wa~ 

i tery,  infipid,  thin,  neither  acrid 
nor  alkaline,  is  excreted  at  the  fame  place  into 
which  the  bile  is  difcharged. 

DCLXXXV  I.  The  pancreas,  the  largefi;  of  the  fali- 
vary  glands,  is  of  great  length,  is  fituated  before  the 
left  renal  capfule  and  the  aorta,  above  the  inferior 
lamina  of  the  tranfverfe  mefocolon  ; (which  beyond 
the  pancreas,  behind  its  fuperior  lamina,  behind  the 
ftomach,  before  the  fpleen,  under  and  behind  the 
liver,  joins  wdth  the  inferior  lamina  ;)  is  of  a flattifii 
triangular  fhape,  with  a light  deprefiion  on  the  up- 
per part,  and  is  covered  with  the  peritonaeum.  Up- 
on it,  being  pofterior  and  inferior,  the  -pofteriof 
fide  of  the  empty  firomach  refts.  The  pancreas  be- 
gins at  the  fpleen  itfelf ; extends  almoft  tranfverfe- 
ly  towards  the  right  fide,  acrofs  the  vertebrae,  at  the 
light  of  which  it  grows  broader,  being  received  be- 
twixt the  fuperior  and  inferior  plates  of  the  tranf- 
verfe mefocolon  (dclix.)  and  is,  finally,  fo  con- 
nected by  its  round  head  to  the  duodenum,  as  to 
ferve  it  for  a mefenterjn  It  is  like  the  falivary 
glands,  compofed  of  round,  hardifli  acini,  connected 
by  a good  deal  of  cellular  fubftance.  Its  veflfels 
are  rather  numerous  than  large,  and  are  derived 
chiefly  from  the  fplenics ; but  on  the  right  fide  it 
is  fupplied  by  thefirfi;  artery  of  the  duodenum,  and 
from  another  which  is  inferior,  and  is  common  to 

the 


Ghap.  XXII. 


P^UnCREAS. 


33^ 

the  duodenum  and  pancreas  ; both  of  v/hich  arife 
from  the  hepatic  artery,  and  of  which  the  former 
inofculates  with  the  latter,  and  both  with  the  me- 
fenteric  artery,  which  alfo  fupplies  conliderable 
twigs  to  this  gland  5 and  minute  branches  come 
from  the  phrenic  and  capfular  arteries.*  The  nerves 
are  not  conliderable,  whence  it  is  little  fenlible  ; 
they  are  derived  from  the  pofterlor  gaftric,  the  he- 
patic and  fplenic  plexufes,  &c. 

DCLxxxvii.  The  du6t  runs  through  the  middle 
of  this  gland,  white  and  tender,  arifing  every  where 
from  an  infinite  number  of  roots,  by  which,  being 
gradually  increafed,  it  emerges  before  the  vena  por- 
tarum  and  mefenteric  artery,  having  received  a larg- 
er branch  from  the  larger  part  of  the  pancreas ; fol- 
lowing the  courfe  of  the  duodenum,  it  arrives  at 
the  fame  part  of  the  duodenum  into  which  the  bil- 
iary du(T  proceeds  ; where,  changing  its  courfe,  it 
defcends,  and  being  extended  into  a finus,  betwixt 
the  coats  of  the  inteftine,  internally  fmooth ; and, 
being  continued,  after  having  received  the  du^lus 
choledochus,  it  opens  in  a particular  fold  in  the 
bottom  of  the  descending  part  of  the  duodenum. 
But  it  not  unfrequently  happens,  that  it  opens  by 
an  orifice  diftind:  from  that  of  the  biliary  dud and 
fometimes  by  two,  of  which  the  one,  the  lower,  is 
diftind  and  lefs  ; but  in  man,  and  in  moft  other 
animals,  it  always  opens  near  the  biliary  dud.  In 
its  orifice  there  is  no  valve. 

DCLxxxviii.  The  quantity  of  fluid  fecreted  is 
uncertain  : but  it  mull  be  very  conliderable,  if  we 
compare  it  with  the  weight  of  the  faliva,  the  pan- 
creas being  three  times  larger,  and  feated  in  a 
warmer  place.  It  is  expelled  by  the  force  of  the 
circulating  blood,  and  of  the  incumbent  vifeera  in 
the  full  abdomen  ; as  the  liver,  llomach,  fpleen,- 
mefenteric  and  fplenic  arteries,  and  the  aorta.  Its 
great  utility  appears  from  its  conflancy,  being 
found  in  almofl  all  animals : nor  is  it  refuted  by 

the 


LIVER. 


, Chap.  XXIIL 


the  few  experiments,  in  which  a part  of  it  was  cut 
out  from  a robuft  animal  without  occahoning 
death  ; bccaufe  the  whole  pancreas  cannot  be  re- 
moved without  the  duodenum  ; for  even  a part 
of  the  lungs  may  be  cut  out,  without  producing 
death,  but  they  are  not  therefore  ufelefs.  Its  cf- 
fcrvefcence  with  the  bile  arifes  from  the  elfecl  of 
the  ligature,  and  of  air  mixed  with  the  inteftinal 
liumour. 

DCLXxxviii.  It  feems  principally  to  dilute  the 
vifcid  cyftic  bile,  to  mitigate  its  acrimony,  and  to 
mix  it  with  the  food.  Hence  it  is  poured  into  a 
place  remote  from  the  cyftic  duel  as  often  as  there 
is  no  srall  bladder.  Like  the  reft  of  the  inteftinal  hu- 

O 

mour,  it  dilutes  and  refolves  the  mafs  of  aliments^ 
and  performs  every  other  office  of  the  faliva. 


C H A P.  XXIII. 


LIVER,  GALL  BLADDER,  AND  BILE. 

Dci.xxxix.  liver,  the  largeft  of  all  the 

I vifeera,  occupies  a large  part  of 
the  abdomen,  above  the  mefocolon  ; and  in  the 
foetus  one  ftill  larger.  Both  above,  and  behind,  and 
before,  and  to  the  right,  it  is  covered  by  the  dia-. 
phragm,  from  which  it  receives  the  peritonieum, 
under  the  denomination  of  ligaments,  chiefly  in 
three  places.  For  on  the  convex  part  of  the  liver, 
from  the  pallagc  of  the  vena  cava  to  the  tranfvcrfe 
furrow  of  the  liver,  the  peritoneum  defeends 
double,  growing  broader  anteriorly,  under  the 
name  of  ligamentum  fufpenforium,  which  dmdes- 
the  greater  right  lobe  from  the  fmaller  left  lobe  ; 
and  diverging,  it  expands  into  a membrane  of  the 
liver,  (dcxxiii.)  white.  Ample,  thin,  like  the  ex- 
ternal coat  of  the  ftomach,  having  cellular  fub- 
ftance  under  it,  by  which  it  is  ioined  to  the  fub- 

ftaiu* 


Chap.  XXIIL 


LIVER. 


xj  -J  i 

fiance  of  the  liver.  To  the  lower  margin  of  this, 
the  umbilical  vein  is  United  ; which,  in  the  adult, 
having  almoft  difapipeared,  leaves  a fibrous  appear- 
ance, with  much  fat.  In  the  extremity  of  the  left 
lobe,  and  on  the  convex  part,  and  not  unfrequently 
at  its  edge,  a membrane  goes  to  the  liver  from  the 
diaphragm  ; which  in  children,  ^nd  in  other  in- 
ftances,  is  frequently  to  the  left  fide  of  the  cefo- 
phagus,  but  in  adults  to  the  right  fide  ; and  always 
conjoined  both  to  the  gullet  and  to  the  fpleen,  when 
the  liver  is  large.  This  is  the  left  ligament.  The 
right  ligament  ties  the  diaphragm'  very  far  back  to 
the  very  thick  right  lobe.  Befides,  but  without  any 
apparent  length,  the  membrane  of  the  right  lobe 
of  the  liver  is  often  conjoined  with  the  diaphragm 
by  cellular  fubftance  in  the  right  lobe,  behind  and 
to  the  right  of  the  oval  lobule,  more  efpecially  in 
bid  fubjects,  for  in  the  foetus  it  is  eafily  feparated  ; 
and  betwixt  the  fufpenfory  and  left  ligament,  there 
intervenes  a production  of  peritonaeum,  in  like  man- 
ner continuous,  refembling  a ligament.  But  alfo 
from  the  kidney,  the  peritonaeum  going  to  the  liv- 
er makes  a reduplication  like  a ligament  ; and  the 
fmaller  omentum,  and  the  continuous  loofe  produc- 
tions of  the  mefocolon  (dclxiii.)  unite  the  liver 
with  the  ftomach,  duodenum  and  colon  ; and  the 
mefocolon  alfo  unites  it  to  the  pancreas.  Thus 
the  liver  is  fufpended  in  the  body  with  firmnefs, 
and  yet  with  confiderable  mobility,  fo  that  it  may 
be  varioufly  agitated  and  depreffed  by  the  dia- 
phragm. The  fame  ligaments  form  the  common 
membrane,  which  covers  the  liver  as  well  as  other 
vifcera. 

Dcxc.  Moreover,  the  inner  concave  furface  of 
the  right  lobe  of  the  liver,  correfponds  with  its  fore- 
part to  the  colon  ; and  with  its  back  part  to  the 
right  kidney  and  renal  capfale,  to  which  it  is  cor- 
neCled  by  cellular  fubftance.  The  middle  finus  is 
contiguous  to  the  duodenum,  which  touches  the 
Y gall 


LiVER, 


Chap.  XXIII. 


33^ 

gall  bladder,  and  that  part  which  conducls  the  great 
blood-velTels.  The  left  lobe  extends  largely  over 
the  ftomach  ; and  frequently,  efpecially  in  younger 
fubjecls,  is  extended  beyond  the  oefophagus  into 
the  left  hypochondrium.  The  lobule  adapts  itfelf 
to  the  fmaller  curvature  of  the  ftomach.  But, 
moreover,  the  pancreas  lies  under  the  liver,  and  the 
right  venal  capfule  is  tied  to  the  part  of  the  liver 
fartheft  to  the  right  by  much  cellular  texture. 

Dcxci.  The  figure  of  the  liver  is  difficult  to  de- 
fcribe.  It  begins  in  the  cavity  of  the  right  h)  po- 
chondrium,  by  a very  thick  folid  protuberance, 
convex  towards  the  diaphragm,  and  hollow  towards 
tlie  colon  and  kidney  ; having  a protuberant  line 
dividing  thefe  concave  furfaces,  which  is  continued 
into  the  longer  appendix  of  the  lobule.  After 
this,  the  liver  grows  gradually  flenderer  and  thin- 
ner, and  is  extenuated,  with  an  almoft  triangular 
ftiapc,  into  a tip,  which  palTes  into  the  left  hypo- 
chondrium, acrofs  the  oefophagus,  in  young  fubjeds, 
as  far  as  the  fpleen  ; but  in  adults,  it  is  often  fhort- 
cr,  and  ends  at  the  oefophagus.  The  edge,  in  which 
the  convex  part  of  the  liver  meets  with  the  con- 
cave one,  is  wholly  in  the  anterior  and  lower  part. 
The  wliole  obtufe  margin  lies  backwards,  d'he 
upper  and  back  part  of  the  liver  is  every  where 
convex  ; fuftains  the  diaphragm  ; and  with  a large 
portion,  which  is  fomevvhat  flatter  towards  the  left 
fide,  it  lies  under  the  heart : but  the  lower  furface, 
varioufly  figured,  refts  upon  the  duodenum,  colon, 
ftomach,  pancreas,  and  right  renal  capfule.  For 
there  are  leveral  fiflures  which  divide  the  furface 
into  different  regions,  which  did  not  efcape  the  no- 
tice of  the  ancients. 

Dcxcii.  The  principal  of  thefe,  the  tranfverfe, 
extends  from  right  to  left,  and  divides  a third  part 
of  the  liver,  beginning  flender  in  the  right  lobe, 
and  growing  broader  towards  the  left.  Before  this 
traniveric  fifture,  there  is  an  excavation  in  the  right 


Chap.  XXIII. 


LIVER. 


339 

lobe  for  the  gall  bladder  ; then  there  is  the  convex 
anonymous  lobe  ; and  then  the  foffa  of  the  umbilical 
vein,  extending  tranfverfely  backwards^  often  cov- 
ered with  the  bridge  that  joins  the  anonymous  to 
the  left  lobe.  Behind  the  great  fulcus  in  the  right 
fide,  there  is  a tranfverfe  eminence,  {lender  at  its 
commencement,  growing  broader  tov/ards  the  right 
and  moderately  hollow,  by  which  the  great  blood- 
velTels  are  conduced  into  the  liver  : the  holknv 
was  by  the  ancients  denominated  the  portae.  This 
joins  the  lobe,  which  I Ihall  next  defcribe,  with  the 
right  lobe.  Then  the  pollerior  lobule,  papillary, 
obtufely  conical,  projects  into  the  little  curvature  of 
the  ftoma'chi  The  thick  roOt  of  this  and  of  the 
former  excavated  eminence,  begins  from  the  con- 
vex part  of  the  liver,  at  the  diaphragm  ; and  in 
the  right  fide,  is  impreffed  with  an  oblique  furrow, 
inclined  to  the  right  fide,  fOr  the  trunk  of  the  vena 
cava,  defcending  from  the  heart  to  the  lumbar  ver- 
tebrae,  and  frequently  covered  by  a confiderable 
portion  of  the  fubftance  of  the  liver,  as  by  a bridge, 
fo  as  to  form  a tube.  The  left  end  of  the  lobule 
is  terminated  by  another  foffa  almoft  ftraight  back- 
wards, but  alfo  inclined  to  the  left ; which  begin- 
ning at  the  extremity  of  the  tranfverfe  one,  termi- 
nates at  the  paffage  of  the  vena  cava  through  the 
diaphragm.  In  this  was  lodged  the  duclus  venoms 
in  the  foetus,  of  which  there  are  ftill  fome  remains 
to  be  perceived  in  the  adult.  All  that  lies  beyond 
this  is  the  left  lobe,  which  is  fimple,  uniformly  con- 
cave below,  fo  as  to  lie  upon  the  ffomach,  and  ex- 
tenuated to  an  edsre. 

Dcxciii.  This  very  large  vifcus  is  proportion- 
ably  fupplied  with  vefl'els,  and  of  various  kinds. 
The  artery,  which  is  indeed  confiderable,  being  the 
greater  and  right  portion  of  the  caeliac,  emerging 
forwards  and  to  the  right,  goes  tranfverfely  before 
the  vena  portarum  • and  after  giving  off  the  fm.all 
coronary  and  the  pancreatico  duodenalis,  the  latter 
Y 2 of 


LIVER. 


Chap.  XXIIL 


i4o 

of  which  is  pretty  large,  the  reft  enters  the  liver,- 
commonly  by  two  branches  ; of  which  the  left 
fupplies  the  umbilical  foffa,  the  venal  duel,  pofte- 
rior  lobule,  with  the  left  and  the  anonymous  lobes, 
and  th&  fufpenfory  ligament ; this  branch  inofeu- 
lates  with  the  phrenic  and  epigaftric  arteries.  The 
right  lies  deeper,  covered  by  the  biliary  duels  y 
goes  to  the  right  and  anonymous  lobes,  and  fends 
off,  in  one  fmall  trunk,  the  cyflic  artery,  which  im- 
mediately dividing  into  two,  is  fpread  both  under 
and  over  the  gall  bladder,  covered  by  its  external 
coat,  and  fupplies  branches  to  the  gall  bladder  and 
biliary  ducts,  and  likewife  many  to  the  liver.  From 
the  left  branch,  or  fom.etimes  from  the  trunk,  a- 
fuperficial  artery  goes  to  the  biliary  duels,  anony- 
mous lobe,  and  glands  of  the  portae.  Befides  the 
caeliac  artery,  not  very  rarely,-  a large  right  branch 
is  produced  from  the  mefenterica  major,  creeping 
behind  the  pancreas  ; this  ferves  inftead  of  the 
right  hepatic  branch  of  tlie  caeliac.  But,  like^^dfe, 
the  greater  coronary,  which  is  the  firfl  twig  of  the 
cadiac,  always  gives  fome  ramifications  to  the  left 
lobe,  and  to  the  foffa  of  the  duftus  venofus ; which 
is  often  very  confiderable.  Thofe  fent  to  the  liver 
from  the  phrenic,  mammaries,  renal  and  capfulary 
arteries  are  fmaller.-  They  communicate  alfo  with 
the  epigaftrics.- 

Dcxciv.  In  the  foetus,  the  umbilical  vein  brings 
a great  deal  of  blood  to  the  liver,  at  which  time  the 
vein  going,  to  the  portse  is  but  fmall.  It  fends 
forth,  while  it  flretches  backwards  through  its  foffa, 
numerous  and  very  large  branches,  each  of  them 
equalling  the  vena  porfarum  in  bignel's  ; at  this 
place  it  is  dilated  into  a tumor,  which  unites  with 
the  left  branch  of  the  vena  portarum.  But  it  fends 
a fingle  branch  through  the  poflerior  part  of  the 
horizontal  foiTa  into  the  vena  cava,  or  into  fomc  of 
its  hepatic  branches ; this  is  called  the  duclus  veno- 
fus. In  the  adult,  indeed,  this  duel  is  obliterated, 

and 


Chap.  XXIII. 


LIVER. 


341 

^ind  the  vena  portarum,  which  has  now  grown  lar- 
ger, fupplies  the  hepatic  branches. 

Dcxcv.  The  vena  portarum  receives  all  the  blood 
of  the  ftomach  (dcxxix.)  of  the  inteftines  and  me- 
fentery  (dcxxxi.)  of  the  fpleen  (dclxxvh.)  omen- 
tum (dccxix.)  and,  laftly,  of  the  pancreas,  at  firft 
into  two  trunks,  the  tranfverfe  fplenic  and  amend- 
ing mefenteric,  and  then  into  one,  which  is  conti- 
nued with  the  mefenterics.  It  is  large,^  compofed 
of  ftrong  membranes,  ftronger  than  thofe  of  the 
vena  cava,  afcends  behind  the  firft  flexure  of  the 
duodenum,  receives  the  veins  from  the  right  fide 
of  the  duodenum,  and  the  fmaller  coronary,  afcends 
to  the  right  in  the  finus  of  the  lobule  of  the  liver 
(dcxcii.)  and  is  afterwards  again  divided  into  two 
large  trunks.  The  right,  which  is  fliorter,  larger, 
and  bifurcated,  having  received  the  cyftic  vein,  goes 
to  its  own  lobe.  The  left  proceeds  through ‘the  re- 
maining part  of  the  tranfverfe  furrow  of  the  liv^er, 
and  fupplies  the  lobule,  the  anonymous  and  left 
lobe,  and  being  refleffed,  enters  the  umbilical  fofla, 
about  the  middle  of  which,  it  penetrates  branchy 
into  the  liver.  There  are  inftances  in  which  the 
branch  of  the  pofterior  lobule  rather  proceeds  from 
the  trunk  of  the  vena  portarum. 

Dcxcvi.  The  vena  portarum  is  furrounded  on 
every  fide  with  a good  deal  of  cellular  fubftance, 
wMch  it  brings  with  it  from  the  mefentery  and 
fpleen  ; and  which  being  denfe  and  flrort,ftrengthens 
the  membranes,  which  are  firmer  than  thofe  of  the 
aorta  itfelf.  Intermixed  with  this  cellular  fubftance, 
are  alfo  many  fmall  yelfels  and  the  hepatic  nerves, 
which  are  all  comprehended  under  the  denomina- 
tion of  capfule,  which  is  nothing  more  than  the 
cellular  fubftance,  and  never  has  a Angle  truly 
flefliy  fibre.  The  vena  portarum  carries  this  along 
with  it,  through  the  liver,  and  is  fuftained  by  it ; 
infomuch,  that  the  branches,  when  cut,  being  fup- 
ported,  preferve  the  roundnefs  of  their  fedion. 

Each 


LIVER. 


Chap.  XXIH. 


34^ 

Each  branch  of  the  vena  portarum  is  divided  into 
many  others,  again  divided  and  fabdivided,  e\'en 
to  the  fmalleft  capillaries,  as  arteries  commonly  are. 
Every  branch  of  the  vena  portarum  is  accompanied 
by  a branch  of  the  hepatic  artery,  creeping  upon  its 
furface,  and  upon  the  hepatic  duels,  almolt  in  the 
fame  manner  as  the  bronchial  arteries  ufually  creep 
along  the  bronchia  ; and  by  a branch  of  the  biliary 
duct,  which  are  both  connecled  by  thin  cellular 
fubftance.  Some  go  out  of  the  liver,  being  divided 
on  the  ligaments,  and  inofculating  with  the  fur- 
rounding veins.  The  fum  of  the  branches  in  the 
vena  portarum  is  alv/ays  greater  than  the  trunk ; 
hence  the  calibers  of  all  the  branches  together, 
greatly  exceed  that  of  the  trunk  (xxxva.')  Hence  ; 
there  is  a great  degree  of  friclion,  (clxxx.  and 
CLXii.}  exactly  as  in  the  arteries. 

Dcxcvii.  But  as  the  blood  is  conveyed  to  the  liver 
by  the  vena  portarum,  as  well  as  by  the  hepatic  ar- 
tery,  it  muft  of  courfe  be  conveyed  away  by  fome 
other  vein.  Therefore,  the  extreme  branches  of 
the  vena  portarum  and  hepatic  artery  inofculate 
ultimately  with  other  veins,  which  are  branches  of 
the  cava  ; arifing  from  the  whole  circumference  of 
the  liver,  they  run  towards  the  pofterior  gibbous 
part  of  the  liver,  unite  into  branches  and  trunks, 
which  at  laft  terminate  in  ten  or  more  large  velfels. 
'I'he  fmaller  and  more  numerous  of  thefe,  arife  from 
the  pofterior  lobule  and  liver,  and  go  to  the  cava, 
where  it  afeends  towards  the  left,  to  the  diaphragm, 
through  the  fulcus,  that  lies  on  the  right  fide  of  the 
lobule,  and  is  often  included  by  a bridge  thrown 
over  it.  The  remaining  two  or  three,  which  are 
much  larger,  are  inferred  into  the  fune  cava,  cirfe 
to  the  diaphragm,  whofe  veins  they  often  receive. 
The  branches  of  the  vena  cava  are,  in  the  adult,  on 
the  whole,  fewer  than  thofe  of  the  vena  portarum  ; ' 

which  is  an  argument  that  the  blood  moves  more 
quieddy  through  thefe  branches,  on  account  of  the 

dinunuti'^u 


Chap.  XXIII. 


LIVER. 


343 

diminution  of  the  friction,  (clxx.)  and  of  the  very 
colleftion  of  the  blood  into  a lefs  caliber,  which 
always  accelerates  its  courfe,  when  there  is  a fufh- 
cient  compreffing  force  (clxx.)  I know  not  of 
any  valves  in  the  mouth  of  thefe  veins,  which  de- 
ferve  to  be  remembered.  The  trunk  of  the  vena 
cava  afcends  through  a foramen  of  the  diaphragm, 
obtufely  quadrangular,  included  by  mere  tendons 
furrounding  it  ; and  therefore  (cclxii.)  not  eafily 
variable  : and  immediately  expands  into  the  right 
auricle.  The  fmaller  veins  of  the  ^iver,  creeping 
upon  its  furface,  are  fent  from  the  phrenica,  rena- 
lis  and  azygos  ; or  at  leaft  there  is  a communication 
betwixt  thefe  and  the  hepatic  veins  coming  from 
the  portae. 

Dcxcvin.  That  the  blood  comes  from  all  parts 
(dcxcv.)  by  the  vena  portarum  to  the  portae,  is 
proved  by  ligatures,  by  which  the  veins  fwell  be- 
twixt thefe  parts  and  the  ligatures ; while  the  vena 
portarum  itfeif  grows  flaccid  and  empty.  But  that 
it  afterwards  goes  through  the  liver  to  the  cava, 
is  proved  by  anatomical  injections,  which  fhow  the 
anaftomofes,  and  open  communication  betwixt  the 
vena  portarum  and  the  cava,  and  by  the  common 
nature  of  the  veins  going  to  the  cava.  Again,  the 
difliculty  of  the  arterial  diftribution  of  the  vena  por- 
tarum, as  being  remote  from  the  heart,  and  the 
oily  nature  of  its  blood,  occafion  it  to  fcagnate,  accu- 
mulate and  form  fcirrhous  fwellings  in  the  liver 
oftener  than  in  any  other  part.  But  this  danger  is 
diminilhed  by  mufcular  action,  and  refpiration  ; 
and  is  increafed  by  reft,  indolence,  and  four  and  vif- 
cid  aliments.  Elitherto,  we  have  been  fpeaking  of 
the  adult  liver,  in  which  both  the  umbilical  vein 
and  the  duclus  venofus  are  empty,  although  they 
cohere  with  the  left  branch  of  the  vena  porta- 
rum. 

Dcxcix.  The  nerves  of  the  liver  are  rather  nu- 
merous  than  large  ; hence,  when  wounded  or  in- 

flapaed. 


LIVER. 


Chap.  XXIII. 


344 

flamed,  it  caufes  a moderate  degree  of  pain.  They 
have  a twofold  origin.  Moft  of  them  arife  from 
the  large  gangliform  plexus  of  the  fplenic  branch 
of  the  intercoftal  nerve,  with  the  addition  of  a 
branch  from  the  pofterior  plexus  of  the  eighth 
pair  ; they  accompany  the  hepatic  artery,  and, 
playing  around  its  trunk,  go  to  the  liver,  with  that 
and  the  branches  of  the , vena  portarum.  Anoth- 
er fafci'culus  of  nerves  ufually  enters  with  the  duc- 
tus venofus,  and  arifes  from  the  pofterior  plexus 
of  the  eighth'pair,  but  fometimes,  from  the  great 
plexus. 

Dcc.  The  lymphatic  veflels  of  the  liver  are  nu- 
merous, and  may  be  conftantly  and  eaftly  feen  about 
the  portae.  They  arife  from  the  whole  concave  fur-; 
face  of  the  liver,  and  from  the  furface  of  the  gall 
bladder,  run  together  into  a plexus,  furrounding 
the  vena  portarum,  and  go  to  the  conglobate  glands, 
feated  before  and  behind  the  faid  vein  j from  whence 
they  meet  together  in  one  large  trunk,  wdrich  is  one 
of  the  roots  of  the  thoracic  duct.  L^pon  the  con- 
vex part  of  the  liver,  are  deferibed  other  lymphat- 
ics, v/hofe  infertion  is  not  well  known  ; for  it  is 
hardly  probable  that  they  enter  the  cava,  nor  have 
they  been  fufticiently  often  traced  to  the  receptacle 
of  the  chyle. 

Dcci.  The  interior  fabric  of  the  liver  is  more  ob- 
feure.  Through  the  whole  liver,  bundles  of  bil- 
iary veflels,  of  branches  of  the  vena  portarum,  and 
of  the  hepatic  artery,  are  diftributed.  Each  vef- 
fel  has  both  its  proper  cellular  texture  furrounding 
it,  and  ligaments  of  the  fame  fubftance,  by  which 
it  is  tied  to  its  fellow  veflels  ; and,  laftly,  the  whole 
bundle  is  furrounded  by  cellular  texture.  The 
branches  of  the  vena  cava  lie  on  the  cutflde  of  the 
others,  being  lefs  accurately  received  into  the  fame 
bundle.  Laftly,  the  ultimate  branches  of  the  ve- 
na portarum,  cava,  and  hepatic  artery,  and  of  the 
biliary  du<5ts,  which  we  Ihall  foon  deferibe,  are  uni- 


LIVER. 


Chap.  XXIII. 


345 


ted  together  by  means  of  cellular  fubftance  (dcxcvi.) 
into  a fort  of  acini  of  a fomewhat  hexagonal  fliape, 
ifurrounded  with  lax  cellular  fubftance.  In  thefe 
bunches,  likewife,  there  are  mutual  anaftomofes  of 
the  branches  of  the  vena  portarum,  and  of  the  he- 
patic artery,  with  the  roots  of  the  vena  cava,  and  of 
the  branches  of  the  vena  portarum,  with  the  firft 
origins  of  the  pori  biliarii ; which  laft  connexion  is 
demonftrated  by  anatomical  injeftions  ; for  liquors 
injected  into  the  vena  portarum,  at  laft  return 
through  the  porus  choledochus. 

Dccii.  Many  eminent  anatomifts  have  taught, 
that  thefe  acini  are  hollo^vvhaving  arteries  and 
veins  fpread  upon  their  external  furface,  and  that 
the  bile,  fecreted  from  the  branches  of  the  vena 
portarum,  is  depoftted  into  their  cavities.  They 
derive  their  arguments  from  the  anatomy  of  brutes, 
in  whofe  liver  the  acini  are  round,  and  more  de- 
fined than  in  man  ; and  from  difeafes,  which  exr 
hibit  cells  and  round  tubercles,  filled  with  lymph, 
chalk,  and  various  kinds  of  concreted  matter.  I'q 
this,  they  might  have  added  the  lentor  of  the  bile, 
by  which  it  refembles  mucus,  and  the  analogy  of 
the  follicles  of  the  gall  bladder. 

Dcciii.  But  greater  accuracy  in  anatomy  does  not 
admit  thefe  follicles  into  which  the  fmall  fecretory 
veflels  are  faid  to  open  ; for  fuch  would  intercept  the 
courfe  of  wax  injecftions,  and  would  occafton  inter- 
mediate knots  betwixt  thefe  veflels  and  the  biliary 
pores,  which  have  never  yet  been  feen  ; for  the  wax 
flows  in  one  continued  thread,  without  any  retar- 
dation, effufion  into  a cavity,  or  diminution  of  its 
impetus,  from  the  vena  portarum  into  the  biliary 
du<fts.  Nor  could  the  great  length  of  the  biliary 
duels  admit  of  a glandular  fabric.  For  all  follicles 
depoflte,  at  no  great  diftance,  their  fluid,  which  is 
not  fitted  for  a long  courfe,  as  they  deftroy  fo  great 
a part  of  the  velocity  received  from  the  arteries. 

Laftly, 


346 


LIVER. 


Cha?.  xxm. 


Laflly,  the  very  common  preffure,  would  fo  crufh 
thefe  bundles  of  acini,  which  vx  mull  fuppofe,  that 
the  motion  of  the  excretory  duel  could  derive  no 
affiftance  from  thence.  The  concretions  and  hy- 
datids are  formed  in  the  cellular  fubfrance ; and, 
laftly,  the  bile,  when  lirft  fecreted,  is  fufficientiy 
fluid. 

DC  CIV.  Again,  we  are  convinced,  that  no  bile  is 
feparated  from  the  hepatic  artery,  by  the  peculiar 
ftruebare  of  the  vena  portarum,  which  would  be 
ufelefs  if  it  fecreted  nothing  ; by  the  continuity 
of  its  branches  with  the  biliary  dufts,  which  is 
much  more  evident  than  in  the  arteries ; by  the 
experiment,  in  which  it  appears  that  the  biliary  fe- 
cretion  continues  after  the  hepatic  arter)’-  is  tied  ; 
by  the  great  fize  of  the  biliary  ducts,  in  proportion 
to  fo  fmall  an  artery,  and  by  the  peculiar  nature  of 
the  blood  collected  in  the  vena  portarum,  which  is 
perfectly  adapted  for  the  iecretion  of  bile.  For  it 
contains  both  oil,  which  abounds  m.ore  in  the  bile 
than  in  any  other  humour  of  the  body  ; and  a fa- 
ponaceous  fluid,  abforbed  from  the  ftomach,  and 
the  alkalefcent  fiibfetid  vapour  of  the  abdomen, 
i'lought  back  from  the  whole  furface  of  the  intef- 
tines,  flomach,  omentum,  liver,  fpleen,  and  mefen- 
ter%',  as  we  know  by  evident  anatomical  experi- 
ments ; and,  finally,  the  alkalefcent  femiputrid,  ac- 
rimonious humidity,  abforbed  from  the  alvine  fe- 
ces themfelves,  while  they  are  indurated  in  the  large 
inteftines,  and  brought  thither  by  the  internal  he- 
morrhoidal veins,  from  whence  that  bitternefs,  al- 
kalefcent and  putrefeent  difpofition  of  the  bile  is 
derived.  But  in  the  blood  of  the  hepatic  arter}', 
there  is  nothing  which  renders  it  peculiarly  fitted 
for  the  fecretion  of  bile,  or  analogous  to  it. 

Dccv.  Since,  therefore,  the  vena  portarum  con- 
veys the  blood,  in  its  fitteft  Rate,  for  the  fecretion  of 
bile,  to  the  ultimate  acini  of  the  liver,  (neen'-,' 
as  there  the  paflage,  from  each  branch  of  the 

ve:.a 


Chap.XXIII. 


LIVER. 


347 

vena  portarum,  into  the  beginning  of  the  biliaiy 
du<fts,  is  diredf  without  any  intermediate  follicle, 
and  as  fluids  injefted  into  the  vena  portarum  read- 
ily take  this  courfe,  the  bile  vdll  be  propelled  that 
way  by  the  force  of  the  blood  furrounding  it,  and 
urging  it  from  behind, and  alfo  by  the  accefibry  force 
of  the  diaphragm  prefling  the  liver  againfl;  the  refl: 
of  the  vifcera  in  the  very  full  abdomen,  (dclxxxix.) 
and  again  of  the  thorax,  contracled  in  exfpiration, 
it  will  be  forced  into  the  larger  branches,  and  laft- 
ly  into  the  two  trunks  of  the  hepatic  biliary  duff  ; 
which  trunks  meet  together  in  one  on  the  vena 
portarum,  and  in  the  tranfverfe  folfa  of  the  liver, 
near  the  anonymous  lobe. 

Dccvi.  This  duel  is  compofed  of  a ftrong  nervous 
membrane,  like  that  of  the  inteftines,  and  of  an 
external  and  internal  cellular  coat,  and  of  a villous 
coat,  loofe,  elegantly  reticulated,  but  afperated  v/itli 
many  fmall  pores  and  flnufes,  and  continuous  wdth 
that  of  the  inteftine.  There  is  no  certainty  of  any 
mufcularity.  From  experiments,  it  appears  to  have 
3 moderate  degree  of  irritability.  That  it  is  vaftly 
dilatable,  is  flaown  from  difeafes.  They  feem  alfo 
to  flaow  that  this  duel  is  pofl'effed  of  great  fenfibil- 
ity.  _ 

DC  evil.  The  hepatic  duel,  thus  formed,  goes 
along  the  vena  portarum,  more  to  the  right  than 
the  artety,  towards  the  pancreas  ; and  then  defeend- 
ing  obliquely,  covered  by  fome  part  of  that  gland, 
it  comes  in  contadl  with  the  back  and  lower  part 
of  the  fecond  flexure  of  the  duodenum,  about  fix 
inches  from  the  pylorus  ; paffes  through  an  interval 
in  its  flslhy  fibres ; meets  vdtli  an  oblique  oblong 
liiius,  made  by  the  pancreatic  du6l,  and  opens  into 
it  by  a narrow  orifice.  This  finus  defeends  oblique- 
ly a long  way  through  the  fecond  cellular  coat,  of 
the  duodenum,  pertprates  the  nervous  coat,  and 
again  runs  obliquely  between  it  and  the  villous  tu- 
nic 5 and,  laflly,  opens  into  a protuberant  long  tail- 
ed 


LIVER. 


Chap.  XXIII. 


34S 

ed  wrinkle  of  the  duodenum.  Between  the  firft  ar- 
rival of  this  duel  at  the  duodenum  and  its  orifice, 
a finus,  almofi;  an  inch  long,  which  receives  the 
duflus  choledochus,  is  inclofed  between  the  mem- 
branes of  the  inteftines,  fo  that  when  this  inteftine 
is  filled,  or  diftended  by  flatus,  or  clofely  contracl- 
ed  by  a violent  periflaltic  motion,  it  muft  be  confe- 
quently  compreffed  and  fhut ; but  when  the  duode- 
num is  relaxed,  and  moderately  empty,  it  difeharges 
itfelf.  Any  regurgitation  from  the  duodenum  is 
hindered  by  this  obliquity,  and  by  the  wrinkle, 
which  is  eafily  prelTed  together,  or  clofed,  and  by 
the  very  eafy  defeeut  of  frefh  bile  through  the  duel. 
Even  air  does  not  find  its  way  from  the  inteftine  in- 
to tlie  duel. 

Dccviii.  But  in  the  very  portae,  this  duel  receives 
the  addition  of  another  lefs  canal  of  the  fame  kind, 
for  a good  way  parallel,  and  adhering  to  it,  and 
inferted  into  it  in  a very  acute  angle.  This  is 
called  the  cyflic  duel,  from  its  origin,  and  is 
fometimes  firfl  increafed  by  another  duct  from 
the  liver.  It  arifes  from  the  gjall  bladder,  which  is 
found  in  moil  animals  ; but  is  abient  in  fome,  efpe-r 
dally  the  fwift  footed,  and  perhaps  only  the  herbi- 
vorous. It  is  contained  in  an  excavation  of  the 
right  lobe  of  the  liver,  (dccxcii.)  to  the  right  of 
the  anonymous  lobule,  in  fuch  a mamner,  that  in 
young  people,  it  lies  entirely  vnthin  the  edge  of 
the  liver,  but  in  adults  projeds  confiderably  be^ 
yond  it,  lying  upon  the  colon.  Its  fituation  is  tranf- 
verfe,  from  before  backwards  ; its  neck  afeends  a 
little. 

Dccix.  The  fismre  of  the  trail  bladder  is  variable, 
but  in  general  like  that  of  a pear  ; it  is  terminat- 
ed before  by  an  obtufe,  hemifpherical,  imperdous 
end  ; and  gradually  diminifhes  backwards ; the  neck 
or  tip  of  this  truncated  cone  being  refiecled  againll 
itfelf  once  or  twice,  and  tied  together  by  proper 
cellular  fubftance  ; and  having  made  another  flex- 
ure upwards,  ends  in  the  cyflic  dud  5 which  from 

thence 


LIVER. 


Chap.  XXIII. 


349' 


thence  goes  towards  the  left  fide  of  the  hepatic  du<d:. 
But  this  dud,  being  alfo  contraded  by  many  cellu- 
lar bands,  is  internally  marked  with  many  protu- 
berant wrinkles,  which,  conjundly  in  the  dried  gall 
bladder,  reprefent  a kind  of  fpiral  valve  ; but  be- 
ing foft  and  alternate  in  the  living  body,  they  re- 
tard, but  do  not  entirely  obftrud,  the  courfe  of  the 
bile  either  way,  as  is  proved  by  experiments,  made 
with  air  and  prelTure.  Befides,  it  is  reticulated  like’ 
the  gall  bladder  itfelf. 

Dccx.  The  outermoft  coat  of  the  gall  bladder  cov- 
ers only  its  lower  fide,  being  the  common  covering 
of  the  liver  itfelf,  ftretched  over  the  gall  bladder, 
and  retaining  it  in  its  fituation.  The  fecond  is 
a loofe  cellular  coat.  The  third  coat  has  fome- 
times  fplendent  longitudinal  fibres,  in  different  di- 
rections, fo  as  obliquely  to  interfect  each  other.  At 
other  times,  it  has  none  j fo  that  w^e  may  doubt  of 
its  mufcular  nature,  efpecially  as  the  irritability  of 
the  gall  bladder  is  flow  and  obfeure.  The  nervous, 
fecond  cellular,  and  villous  coats,  are  found  as  in 
the  inteftines,  except  that  the  laft,  as  in  the  biliary 
duds,  is  reticulated  and  full  of  cells.  In  the  gall 
bladder,  efpecially  about  its  neck,  but  even  as  far  as 
its  middle,  we  obferve  muciferous  pores,  capable  of 
receiving  a briftle  ; and  arteries,  as  in  other  places, 
difeharge  fome  watery  humour  into  the  cavity  of 
the  gall  bladder,  and  bile  eafily  tranfudes  through 
inorganic  pores  to  the  furface  of  the  gall  bladder, 
and  neighbouring  membranes. 

DC  CXI.  Ail  animals,  between  their  gall  bladder 
and  liver,  or  between  their  duds,  have  alfo  fome 
peculiar  openings  into  the  gall  bladder,  into  which 
fome  duds,  originating  from,  the  liver,  or  from  the 
hepatic  biliary  dud,  open.  In  man,  fimilar  duds 
have  not  been  fhowm  by  any  certain  experiment,  and 
the  gall  bladder,  when  full  of  bile,  is  eafily  fepara- 
ted  from  the  liver,  wdthout  a drop  of  bile  efcaping 
either  from  it  or  from  the  liver.  There  is  alfo  a 


LIVER. 


3 5-5 


Chap.  XXIII. 


thin  water  in  the  bladder  as  ofterx  as  the  cyftic  dudt 
is  obftrucced. 

Dcexii  The  bile  naturally  flows  both  out  of  the 
bladder  and  liver,  whenever  there  is  no  impediment 
in  its  courfe  ; fo  that  both  duels  fwell  when  tlie  paf- 
fage  is  obftru6led,  and  the  cyftic  lies  in  a ftraight 
line  with  the  choledochus.  Nor  is  it  probable  that 
the  whole  of  the  bile  is  fent  into  the  gall  blad- 
der before  it  flows  into  the  duodenum.  There  is 
not  a perpetual  obftacle  which  hinders  its  efilux, 
and  peculiarly  obftrucls  the  hepatic  bile,  and  ad- 
mits the  cyftic  ; the  paflage  into  the  duclus  chole- 
dochus is  larger  and  ftraighter,  the  duclus  cyfticus 
much  lefs  than  the  hepatic,  and  therefore  not  form- 
ed for  receiving  all  the  bile  ; the  choledochus,  much 
larger  than  the  cyftic,  and  therefore  not  appointed 
for  the  reception  of  its  bile  only.  There  are  many 
animals  in  which  the  hepatic  duel  enters  the  in- 
teftine  without  any  communication  with  the  cyf- 
tic. In  living  animals,  even  when  the  cyftic  dueft 
is  free,  the  bile  appears  to  defeend  into  the  duode- 
num with  a perpetual  current.  That  the  quantity 
is  very  confiderable,  appears  from  the  magnitude  of 
the  fecretory  organ,  and  of  the  excretory  duel, 
which  is  fo  many  times  larger  than  the  fdivary 
ones  ; from  difeafes,  in  whicli  four  ounces  of  cyftic 
bile  only  have  flowed  out  daily  through  an  ulcer  of 
the  ftde.  But  the  hepatic  bile  goes  into  the  gall 
bladder,  as  often  as  there  is  any  obftruclion  in  the 
duodenal  iinus,  from  flatus,  or  any  other  caufe  ccm.- 
prefling  the  orifice  of  the  duclus  choledochus.  Ac- 
cordingly, it  is  found-  extremely  full,  whenever  the 
common  biliary  duel  is  comprefted  by  any  feirrho- 
fity  or  tum-our,  and  it  is  fometimes  enlarged  beyond 
all  belief ; if  the  cyftic  dull  be  tied,  it  fwells  be- 
twixt the  ligature  and  its  union  with  tlie  hepatic 
duel ; and  in  living  animals,  the  hepatic  bile  has 
been  feen  to  diftU  into  the  wounded  gall  bladder. 
This  is  not  inconuftent  with  tlic  retrograde  angle- 

t T 


Chap.  XXIIL 


LIVER. 


351 

foP  a very  flight  preflure  urges  the  bile  from  the 
liver  into  the  gall  bladder  ; and  air  eafily  takes  the 
fame  way,  more  efpecially  if  the  duodenum  be  firtl 
inflated.  Nor  does  there  fcem  to  be  any  other  bile 
fecreted  by  the  gall  bladder.  Whenever  the  cyftic 
dud  is  obftruded  by  a calculus,  or  by  a ligature 
made  upon  it,  we  find  nothing  in  the  gall  bladder, 
except  a fmall  quantity  of  iniipid  mucus,  fecreted 
from  the  follicles,  (dccx.)  or  fome  watery  exhala- 
tion. In  many  animals,  we  meet  with  no  appear- 
ance of  a gall  bladder,  when,  neverthelefs,  plenty 
of  acrid  and  falutary  bile  is  difcharged  into  the  in- 
teftines.  It  does  not  feem  probable,  that  any  bile  is 
fecreted  in  the  gall  bladder  from  the  cyftic  branch 
of  the  vena  portarum,  for  that  is  a mere  returning 
veflel ; nor  from  the  hepatic  artery,  for  it  is  fcarce- 
ly  probable,  that  the  very  acrid  cyfiic  bile  fhould 
be  feparated  from  a milder  blood  than  milder  hepa- 
tic bile  prepared  from  appropriated  blood  (ncciv.) 

Dccxii.  Laftly,  the  bile  flows  aifo  from  the  gali 
bladder  to  the  liver,  and  at  length  returns  into  the 
blood,  when  its  pafl’age  into  the  inteftines  is  totally 
intercepted,  fometimes  alfo  from  a latent  caufe  exift- 
ing  in  the  nerves.  This  courfe  is  morbid,  and  pro- 
duces the  jaundice  ; which,  therefore,  is  cured  by 
the  paiTage  of  the  calculi,  and  by  reftoring  its  free 
courfe. 

Dccxiii.  Therefore,  a portion  of  the  hepatic  bile 
being  received  into  the  gall  bladder,  ftagnates,  be- 
ing only  gently  agitated  by  refpiration,  and  there 
exhales  its  thinner  parts,  which  we  fee  extenfively 
diffufed  over  the  adjacent  membranes.  The  re- 
mainder, being  oily  and  fubalkaline,  from  its  warm 
situation,  grows  acrid  and  rancid,  and  its  thicknefs, 
bitternefs,  and  colour  are  increafed  ; nor  is  there 
any  other  difference  betwixt  the  cyfUc  and  hepatic 
bile,  which  lafl:  we  find  in  the  duels,  lefs  bitter,  lefs 
dark  coloured,  and  lefs  vifeid.  That  this  difference 
proceeds  only  from  ftagnation,  appears  from  fuch 

animals 


LIVER. 


Chap.  XXIIL 


352 

animals  as  have  only  a larger  porus  hepaticus,  in- 
ftead  of  a gall  bladder  ; for  the  bile  which  ftagnates 
there,  is  remarkably  more  bitter  than  that  in  the  liv- 
er ; as,  for  example,  in  the  elephant.  But  the 
gall  bladder  gives  this  particular  advantage,  that  it 
receives  the  bile,  when,  the  ftomach  being  empty, 
it  is  of  no  ufe,  and  fupplies  it  more  quickly  when 
we  principally  Want  it  for  the  digeftion  of  the  ali- 
mcnts,  now  flowing  in  great  quantity  into  the  duo- 
denum. This  quicknefs  is  greater  in  proportion  as 
the  cylfic  duel  is  fmaller  than  the  gall  bladder. 

Dccxiv.  The  gall  bladder,  indeed,  does  not  touch 
the  flomach,  but  the  beginning  of  the  defeending 
duodenum.  But  when  the  ftomach  is  diftended, 
and  occupies  a confiderable  fpace  in  the  very  full 
abdomen,  it  both  preftes  the  liver  and  duodenum, 
and  comprefles  the  gall  bladder,  and  empties  it. 
Thus  the  bile  flows  through  a free  paflage,  from 
the  gall  bladder  into  the  biliary  duel,  and  into  the 
duodenum  5 moft  eafily  in  perfons  lying  on  their 
back,  for  then  the  bottom  of  the  gall  bladder  is  up- 
permoft.  Hence  the  gall  bladder  becomes  turgid 
after  fafting.  There  is  fcarcely  any  other  evacua- 
ting power  than  the  ftomach  and  diaphragm  ; for 
that  reflding  in  the  proper  mufcular  and  contractile 
membrane  of  the  gall  bladder,  is  very  inconlidcr- 
able. 

Dccxv.  The  hepatic  bile  is  always  bitter,  but 
the  cyftic  more  fo  ; always  vifeid  ; of  a full  yellow 
colour,  with  a tinflure  of  green  ; mifciblc,  by  tritu- 
ration, with  wa'ter  and  oil,  and  with  \dnous  fpiritsr 
coagulable  by  the  mineral  acids  ; foluble  in  the 
alkalies,  efpecially  the  volatile  alkali ; well  adapted 
for  diflblving  oily,  refinous,  or  gummy  fubftances  j 
of  a lixivial  and  faponaceous  nature  ; quickly  pu- 
trefying, and  by  putrefadlion  fpontaneoufly  acquir- 
ing the  odour  of  muik.  Its  chemical  analyfls,  and 
experiments  of  mixture  with  various  fabftances,  de- 
monftrate,  that  it  contains  a large  portion  of  water. 


Chap.  XXIIL 


LIVER. 


353 

and  a confiderable  quantity  of  the  inflammable  oil, 
which  is  fo  evident  in  cyflic  calculi.  It  therefore, 
is  a foap  ; but  of  that  fort  which  is  compofed  of  a 
volatile  alkaline  fait,  m.ixed  with  oil,  and  retains  its 
water.  Therefore,  being  intermixed  with  the  ali- 
ment, reduced  to  a pulp  and  exprefled  from  the 
ftomach  by  the  periftaltic  motion  of  the  duodenum, 
and  preflure  of  the  abdominal  mufcles,  it  in  a great 
meafure  overcomes  the  acefcent  qualities  of  the 
food  ; it  diflblves  the  coagulum  of  milk,  and  dif- 
pofes  the  aliment  more  to  putrefcency  ; it  diflblves 
the  oily  matters,  fo  that,  by  freely  incorporating 
with  the  watery  parts,  they  may  form  chyle,  and 
enter  the  lacteals  ; it  abflerges  and  attenuates  the 
mucus  ; and,  laftly,  excites  the  periftaltic  motion 
ty  its  acrimony  ; all  which  offices  are  confirmed, 
by  obferving  the  oppofite  difeafes  to  arife  from  a 
want  of  bile.  Nor  is  the  hepatic  bile  ftifficient  to 
evacuate  the  inteftines,  if  the  cyftic  is  wanting.  So 
great  is  its  utility,  that  perfe<ftly  robuft  animals 
have  been  found  to  die  in  a few  days,  by  prevent- 
ing the  afflux  of  bile  to  the  inteftines,  or  deftroying 
the  gall  bladder. 

Dccxvi,  The  bile  gradually  defcends  along  with 
the  food,  and  is  evacuated  along  with  the  faeces, 
fomewhat  changed,  its  bitternefs  being  deftroyed 
by  putridity.  Perhaps  fome  of  the  watery,  leaft 
bitter,  and  thinneft  parts,  are  again  taken  up  by  the 
vena  portarum.  Its  regurgitation  into  the  ftomach 
is  impeded  by  the  afcent  of  the  duodenum,  at  the 
bottom  oif  which  it  enters,  by  the  valve  of  the  py- 
lorus, and  by  the  accefs  of  new  chyle  which  the  fto- 
mach adds  to  the  former : in  man,  however,  it  fre- 
quently happens,  and  in  birds  always.  The  bile  in 
the  foetus  is  bland  and  fweet ; for  in  them  no  fetid 
fasces  fupply  acrid  alkaline  vapours,  nor  is  there 
any  oil  abforbed.  As  the  bile  is  vifcid  in  fluggilh 
and  fat  animals,  and  in  man  from  the  fame  caufes, 
and  from  grief,  it  readily  forms  hard  coagulums, 
Z either 


INTESTINES. 


Ghap.  XXIV- 


354 

either  calcareous  or  refinous,  and  much  more  fre- 
quently than  the  urine,  according  to  our  experi- 
ments. Its  ufe  is  manifeft,  as,  by  trituration  with  the 
aliments,  it  dilfolves  oil,  refifts  acidity,  and  ftimu- 
lates  the  inteftines  to  contraction. 

uccxvii.  In  the  fetus,  behdes  fecreting  the  bile, 
the  ufe  of  the  liver  is  evidently  to  tranfmit  the  blood 
returning  from  the  placenta,  and,  as  it  feems,  to 
moderate  its  impetus.  Even  in  the  adult,  it  has  the 
fame  ufe,  though  lefs  manifeftly,  in  retarding  the 
return  of  the  blood  coming  back  from  the  chylo- 
poetic  vifcera. 

CHAP.  XXIV. 

SMALL  INTESTINES. 

Dccxviii.  1~)  Y the  fmall  inteftines,  anatomifts  un- 

derftand  one  continued,  and  almoft 
cylindrical  tube,  whofe  tranfverfe  fecHon  is  nearly 
oval,  the  obtufe  end  being  towards  the  unconnecled 
fide  of  the  inteftine.  This  tube  being  continued  for 
a long  w^ay  from  the  end  of  the  ftomach,  the  right 
orifice  of  wEich  it  embraces,  (dcxxv.)  terminates  by 
expanding  into  a larger  inteftine.  Anatomifts  have 
uftially  reckoned  three  fmall  inteftines,  though  na- 
ture has  formed  but  one.  However,  the  duodenum 
has  a tolerable  fixed  limit,  at  the  bottom  of  that 
part  of  the  abdomen  which  is  above  the  tranfverfe 
mefecolon  (dclix.)  But  that  fmall  inteftine  which 
lies  below  this  mefocolon,  has  no  certain  mark  of 
diftinclion,  by  which  the  jejunum,  commonly  fo 
called,  is  feparated  from  the  ileum  : for  although 

the  former  abounds  more  with  valves  and  blood-vef- 
fels,  and  is  furniflied  with  longer  villi,  and  there 
fore  appears  fomewhat  redder  ; and  the  ileum  again  ! 
rather  contains  glands,  and  has  fewer  vafcular  ram- 
ifications j thefe  differences  inienfibly  occur,  with- 
out 


I^TTESTINES. 


Chap.  XXIV. 


out  any  certain  limits,  being  great  in  tlieir  extremcj 
and  obfcure  in  their  contiguous  terminations. 

DccxiXi  The  duodenum  is  denominated  from  its 
length.  It  is  lax  and  large,  efpecially  in  its  firft 
flexures^  becaufe  in  part  it  has  no  external  mem- 
brane, and  in  part  is  not  completely  furrounded  by 
it.  It  is  florid  and  tender,  and  has  flefhy  fibres  of 
confiderable  thicknefs.  It  begins  by  adhering  round 
the  annular  orifice  of  the  pylorus  ; then  it  proceeds 
undulating,  but  on  the  whole  tranfverfe,  to  the  right 
and  backwards  in  the  empty  flomach,  to  the  gall 
bladder,  to  the  neck  of  which  it  becomes  conti- 
guous (dccXiv.)  From  thence  it  defcends  oblique= 
ly  to  the  right,  and  backwards  as  far  as  the  lower 
plate  of  the  mefocolon,  and  the  entrance  of  the  bil- 
iary duct,  and  in  that  courfe  is  received  betwixt 
the  upper  and  lower  plates  of  the  mefocolon.  From 
thence  it  again  returns,  tranfverfely,  but  at  the  fame 
time  afcCnding,  behind  the  pancreas  and  large  me- 
fenteric  veffels,  to  the  left,  along  with  the  left  renal 
vein  ; it  goes  out  from  the  duplicature  of  the  plates 
of  the  mefocolon ; and  making  a turn^  it  defcends 
on  the  right  of  the  faid  veffels,  through  a peculiar 
foramen,  in  which  the  mefentery,  left  and  tranf- 
verfe mefocolon,  adhere  to  it,  to  the  lower  part  of 
the  abdomen,  which  it  enters,  and  becomes  the  je- 
junum. The  largenefs  of  this  intefline,  its  afcent 
from  the  infertion  of  the  biliary  duff,  its  fucceeding 
flexure  around  the  root  of  the  mefentery,  caufe  fome 
delay,  by  which  the  bile  and  pancreatic  juice  are 
here  efpecially  mixed  with  the  alimentary  mafs. 

Dccxx.  In  the  reft  of  the  fmall  inteftine  there  Is 
no  certain  point ; but  with  uncertain  and  infinite 
convolutions,  not  to  be  defcribed,  it  fills  the  lower 
part  of  the  abdomen  and  the  pelvis,  furrounded  by 
the  colon,  and  alfo  lies  between  the  bladder  and 

I 

I uterus. 

Dccxxi.  The  fabric  of  the  fmall  inteftine  is  aft 
moil  the  fame  with  that  of  the  ftomach  and  cefo- 
z 2 phagus. 


INTESTINES. 


Chap.  XXIV' 


35^ 

phagus.  Excepting  part  of  the  duodenum,  it  re- 
ceives an  external  coat  from  the  peritonaeum,  or 
mefenter}g  applied  to  the  acute  vertex  of  the  intef- 
tine,  double,  and  feparated  there  by  fome  cellular 
fubftance,  often  by  fat,  but  clofely  embracing  the 
reft  of  the  inteftine,  fo  that  its  mufcular  fibres  ad- 
here to  the  external  membrane,  which  does  not  at 
all  differ  from  that  of  the  ftomach.  By  this  exter- 
nal membrane,  and  by  the  mefentery  (dclxi.)  the 
inteftines  are  fupported  as  firmly  as  is  neceffary, 
and  with  very  great  mobility. 

Dccxxin  But  the  mufcular  coat  is  different,  from 
the  difference  of  figure.  The  moft  confiderable 
ftratum  of  fibres  in  the  inteftines  is  circular  ; they 
furround  the  tube  on  every  fide,  and  are  uniform, 
parallel,  formed  of  imperfecl  arches,  cemented  into 
circles,  pale,  and  yet  remarkably  contractile.  The 
longitudinal  fibres  are,  in  the  I'mall  inteftines,  few 
in  number,  and  fcattered  round  their  whole  extent, 
but  efpecially  laid  over  the  others  on  the  obtufe 
vertex  of  the  inteftine. 

occ XXIII.  Within  the  mufcular  coat,  is  feated 
the  fecond  cellular,  larger,  as  in  the  ftomach,  fpread 
on  all  fides  round  the  nervous  coat,  and  in  man 
rarely  fat.  But  the  nervous  coat,  as  in  the  ftomach, 
ferves  as  the  foundation  for  the  v'hole  inteftinal 
tube  ; it  is  compofed  of  compacted  fibres,  which,  by 
inflation,  may  be  feparated  and  difunited,  fo  as  to 
afl'ume  a cellular  appearance.  Next  follows  the 
third  cellular  coat,  which  is  almoft  like  the  fecond. 
The  innermoft,  the  villous,  differs  from  that  which 
we  defcribed  in  the  ftomach  : for,  firft,  it  is  every 
where  folded  into  wrinkles,  generally  femicircular, 
but  alfo  into  others  joining  the  femicircular  ones 
obliquely,  and  into  others  varioufly  irregular,  into 
which  the  nervous  coat  flightly  enters,  but  the  third 
cellular  enters  deeply,  lying  between  the  doubled 
villous  coat,  and  fiUing  up  the  duplicature.  Thefe 
folds  begin  within  one  inch  of  the  pylorus,  and  are 

moft 


Chap.  XXIV. 


INTESTINES. 


357 

moft  numerous  in  the  firft  half  of  the  inteftines, 
dut  gradually  diminilh  in  number.  In  each  of  thefe 
a fmall  artery  and  vein  lie  upon  the  convex  furface 
of  its  fecond  cellular  coat.  The  firft  plicae  in  the 
duodenum  are  confufed,  and  lie  nearly  in  the  di- 
rection of  the  inteftine.  They  are  changed  into 
acute  circles  and  valves  by  anatomical  preparation. 
They  are  indeed  foft,  and  eafily  inverted,  and  yield 
to  the  paflage  of  the  alimentary  pulp  either  way, 
but  by  their  number  they  retard  it,  and  enlarge  the 
furface  of  the  villous  membrane. 

Dccxxiv.  Laftly,  the  membrane  is  here  truly  vil- 
lous, which  in  other  parts  is  fo  named  from  analo- 
gy. Namely,  the  whole  internal  furface  of  the  in- 
teftine, both  the  valves,  and  the  intervening  hol- 
lows, fend  out  every  where  innumerable  pendulous 
flocculi,  refembling  filk  velvet,  which  are  conical, 
but  fomev/hat  obtufe,  produflions  of  the  inner  coat 
of  the  inteftine,  containing  cellular  fubftance  be- 
tween the  duplicature,  and  veflels  and  nerves  wrap- 
ped up  in  that  fubftance,  and  likewife  a lafteal  vef- 
fel,  fuch  as  we  lhall  afterwards  defcribe,  fo  as  very 
much  to  refemble  the  papillae  of  the  tongue,  except 
in  being  fofter. 

Dccxxv.  The  chief  veflTel  of  each  of  the  villi  is 
an  oval  vcflel,  opening  by  a flender  duct  in  the  fur- 
face of  the  villous  coat,  often  filled  with  a milky 
fluid,  and  furrounded  by  neighbouring  veffels. 

Dccxxvi.  In  the  internal  furface  of  this  villous 
coat,  open  an  infinite  number  of  pores ; fome  larg- 
er, others  fmaUer.  The  former  lead  to  confpicuous 
fimple  mucous  glands,  featcd  in  the  third  cellular 
ftratum,  fimilar  to  thofe  feated  in  the  mouth  and 
pharynx,  having  a very  vafcular  follicle,  and  an  ori- 
fice opening  into  the  inteftine,  In  the  duodenum 
there  are  feveral  of  them  which  are  contiguous,  but 
do  not  run  together,  and  cannot  always  be  demon- 
ftrated ; in  the  ileum  they  are  very  numerous,  both 
folitary,  a few  joined  together,  and  in  confiderable 

numbers 


INTESTINES. 


35S 


Chap.  XXIV. 


numbers  collecled  into  an  elliptical  figure.  They 
are  furroundecj  by  villous  membrane. 

Dccxxvii.  The  fmaller  pores  are  found  through- 
out the  whole  inteftines,  and  furround  the  bafis  of 
the  yiili ; they  are  moft  confpicuous  in  the  large 
Inteftines,  where  they  have  been  long  known,  but 
have  been  lately  difcovered  in  the  fmall  inteftines 
Tkewife.  Thefe  alfo  feem  to  depoftte  a liquor  of 
the  mucous  kind. 

Dccxxviii.  The  veftels  of  the  fmall  inteftines  are 
very  num.erous.  The  common  larger  trunk  belongr 
ing  to  that  part  of  the  inteftine  that  lies  below  the 
mefocolon,  is  called  the  mefenteric  artery,  which  is 
the  largeft  of  thofe  produced  by  the  aorta,  and  fit- 
uated  above  the  renal  arteries.  Defcending  behind 
the  pancreas,  to  the  riglit  of  the  beginning  of  the 
jejunum,  and  beftdes  the  colic  branches,  being  efpe- 
cially  produced  in  a long  trunk  towards  the  right, 
to  the  bottom  of  the  mefentery  and  termination  of 
the  ileum,  it  fends  numerous  branches  from  its  left 
lide,  the  firft  and  laft  being  fliorter,  the  middle  ones 
longer.  Thefe,  fubdividing  into  fmaUer,  join  with 
thofe  adjacent  into  convex  arches  ; which  again 
fend  out  other  branches,  united  in  like  manner, 
forming  almoft  five  feries  of  arches,  until  the  laft 
fend,  from  their  convexities,  ftraight  and  very  nu- 
merous branches  to  the  inteftine. 

Dccxxix.  The  diyifion  of  thefe  branches  on  the 
inteftine,  is  very  uniform  ; fo  that  from  the  mefen- 
tery, through  the  firft  cellular  coat,  there  is  fent 
one  anterior,  and  another  pofterior,  which,  having 
given  fmaU  branches  to  the  outermoft  and  flefhy 
coats,  penetrate  to  tlic  feccnd  cellular  one  : there 
the  anterior  trunk,  running  out  towards  the  obtufe 
vertex  of  the  inteftinal  ellipiis,  is  continued  ftraight 
into  the  correfponding  pofterior  branch  ; and,  ac- 
cording to  its  fize,  gradually  fends  off  fmaller  ar- 
bufcuiar  branches,  inofculating  with  the  contiguous 
and  oppofite  branches,  by  innumerable  twigs.  From 


INTESTINES. 


Chap.  XXIV. 


359 


this  reticulation,  branches  penetrate  through  the 
nervous  tunic  into  the  third  cellular  ftratum,  and 
laftly  into  the  cavities  of  the  villi,  which  finally, 
with  open  orifices,  exhale  their  contents  into  the 
inteftine.  This  courfe  is  eafily  imitated,  by  injec- 
tions of  water,  fize,  or  mercury.  From  recent  ob- 
fervations,  it  has  been  added,  that  the  arterial  ex- 
tremities open  into  an  hollow  veficle,  and  there  de- 
pofite  their  liquor,  which  exudes  through  the  com- 
mon orifice  of  the  veficle.  Befides,  the  reticular 
difpofition  of  the  arteries,  and  their  numerous  anaf- 
tomofes,  have  the  effedl,  that  the  inteftines  are  as 
little  fubjefl  to  obftru6lions  as  poffible,  and  that 
any  obftrucling  matter  may  eafily  return,  by  means 
of  fo  many  inofculations,  into  the  larger  arterial 
trunks. 

bccxxx.  Thelaft  trunk  of  the  mefenteric  artery 
ihofculates  with  the  ileo-colic.  The  duodenum  has 
various  arteries.  The  firft,  the  uppermofi:  from  the 
hepatic,  on  the  right,  goes  round  the  convexity  of 
the  curvature  of  this  inteftine,  in  the  pancreas,  and 
fupplies  this  inteftine,  and  inofculates  with  another 
on  the  left,  and  inferior,  the  pancreatico  duodenalis 
which  makes  a fimilar  arch  in  the  pancreas,  in  the 
hollow  of  the  curvature  of  the  duodenum,  and  is 
at  laft  inferted  into  the  lower  duodenal  arteries,  pro- 
duced by  the  mefenteric  in  its  pafiage  before  this 
inteftine.  I willingly  pafs  over  the  fmall  arteries, 
which  go  from  the  fpermatics  to  the  duodenum, 
and  from  thofe  of  the  renal  capfule. 

Dccxxxi.  The  veins,  exaftly  correfponding  with 
the  arteries,  meet  all  together,  into  the  mefenteric 
trunk  of  the  vena  portarum  ; except  the  right  duo- 
denal vein,  which  goes  immediately  into  the  trunk 
of  the  vena  portarum  itfelf ; and  thofe  fmall  veins 
which  accompany  the  fmaU  arteries,  (dccxxx.)  and 
are  inferted  into  the  fpermatics  and  luinbals.  Nor 
have  I hitherto  been  able  to  difcover  any  other  veins 
of  the  mefentery,  arifing  from  the  cava.  It  is  a pro- 
perty 


INTESTINES. 


Chap.  XXIV. 


36© 

perty  common  to  all  thefe  veins  to  be  without 
valves,  and  to  communicate  freely  with  the  arte- 
ries. In  the  villous  coat,  which  is  for  the  moft  part 
compofed  of  veins,  as  the  venous  trunks  are  fewer 
and  larger,  they  abforb  from  the  inteftines  a thin 
humour  ; as  appears  from  the  inieclion  of  waterv’’  li- 
quors, which  readily  take  that  courfe  ; and,  from 
analogy,  in  aged  perfons,  in  whom  the  mefenteric 
glands,  and  confequently  the  palTage  of  the  lacteals, 
are  frequently  obliterated,  and  from  the  analogy  of 
birds,  which  have  no  lacteals,  and  from  the  celerity 
with  which  watery  liquors  pafs  to  the  blood  and 
through  the  kidneys,  compared  with  the  fmallnefs 
of  the  thoracic  du(T,  and  chiefly  from  thofe  experi- 
ments which  have  confirmed  by  ocular  demonflra- 
tion  the  pafTage  of  water  from  the  cavity  of  the  in- 
teftine  into  the  vena  portarum. 

Dcc:i:xxii.  The  nerves,  numerous  and  fmall,  im- 
part to  the  inteftines  a confiderable  degree  of  fenfi- 
bility ; they  arife  from  the  middle  plexus  of  the 
fplenic  nerves,  which  embraces  the  mefenteric  ar- 
tery, and  play  round  it  in  great  numbers,  wrapped 
up  in  a very  denfe  cellular  fubftance.  The  duode- 
num has  llkewifc  nerves  from  the  pofterior  hepatic 
plexus  of  the  eighth  pair.  From  the  acute  fenfibil- 
ity  of  the  inteftines,  it  is  probable,  that  the  ulti- 
mate branches  of  the  nerves  penetrate  into  the  third 
cellular  coat. 

Dccxxxiii.  From  the  exhaling  arteries,  a thin 
aqueous  liquor  diflils  into  the  cavity  of  the  intef- 
tines, refembling  the  gaflric  juice,  not  acrid,  but 
faltifli.  The  very  great  quantity  of  this  liquor  is 
computed  from  the  great  fize  of  the  excretory  ori- 
fices, and  of  the  fecreting  arteries,  which  are  not 
larger  in  any  part  of  the  body ; and  from  the  lax- 
ity of  parts  perpetually  kept  warm  and  moifl,  and 
from  the  copious  diarrhoeas  or  watery  difeharges 
that  often  follow  the  ufe  of  purgative  medicines. 

Pi;: 


INTESTINES. 


.Chap.  XXIV. 


361 


But  the  mucus  arihng  from  the  fources,  dccxxvi. 
Dccxxyii.  lubricates  the  internal  furface  of  the  vil- 
lous membrane,  and  defends  the  fenlible  nerves  from 
acrid  or  fpirituous  alimentary  matters.  Hence,  it 
is  more  abundant  at  the  beginning  of  the  large  in- 
teftines,  becaufe  there  the  mafs  of  aliment  begins 
to  be  feculent,  acrid,  and  tenacious. 

Dccxxxiv.  This  liquor  is  mixed  with  the  pul- 
py mafs  of  the  aliment,  with  the  bile,  and  with 
the  pancreatic  juice,  by  the  external  motion  of  the 
mufcles  furrounding  the  abdomen  ; but  this  force 
is  quite  fmall,  and  unfit  for  moving  forwards  the 
aliments.  And  in  the  firft  place,  the  periftaltic  mo- 
tion  is'  not  any  where  llronger,  or  miore  evident, 
than  in  the  fmaU  inteflines.  For  any  part  of  the 
inteftine,  irritated  by  flatus,  or  any  fliarp  or  rough 
body,  contra(Ts  itfelf,  even  after  death,  very  vio- 
lently in  that  part  where  the  ftimulus  is  applied, 
frees  itfelf  from  the  offending  or  diftending  body, 
and  expels  it  into  the  contiguous  part  of  the  lax  in- 
teftine ; which  alfo  contracting  from  the  fame  ftim- 
ulus, repels  what  it  received,  either  way.  This 
motion  occurs  in  various  parts  of  the  inteftines, 
without  any  certain  order,  wherever  flatus  or  ali- 
mentary matter  act  as  ftimuli.  So  great,  however, 
is  the  aptitude  of  the  inteftines,  for  motion,  that 
they  emulate,  and  even  exceed,  the  irritability  of 
the  heart,  or  at  leaft  are  fcarcely  exceeded  by  it. 
When  not  irritated,  they  remain  at  reft,  as  I have 
often  obferved  ; and  we  may  fuppofe  this  to  be  the 
caufe  why  fat  retards  the  belly.  The  air  is  the  prin- 
cipal ftimulus  of  the  inteftines,  next  the  aliment, 
and  laftly  the  bile.  This  m.otion  is  performed  by  a 
wonderful  fort  of  alternate  creeping  and  revolution 
of  the  inteftines,  which  difledion  eafily  demon- 
ftrates  in  living  animals,  and  unfortunate  cafes  of 
wounds  in  the  abdomen,  and  ruptures,  have  fhowii 
in  the  human  fpecies.  And  fince,  here,  among  fo 
many  inflexions,  gravity  can  have  no  effect,  the  in- 
teftine 


DH'ESTINES. 


Chap.  XXIV. 


3^2. 

teiline  when  irritated,  evacuates  itfelf  equally  up- 
wards and  downwards.  From  this,  the  antiperifrai- 
1-ie  motion  is  underftood,  by  which  the  pulp  of  the 
aKmentary  mafs  is  longer  expofed  to  the  gentle  trit- 
uration of  the  inteftine,  and  to  the  action  of  the  di- 
luent liquor,  and  of  the  abforbing  veins.  All  the 
contents  of  the  inteftines  are  at  laft  determined  to 
the  large  inteftines,  becaufe  every'  ftimulus  begins 
in  the  left  orifice  of  the  ftomach  ; and  the  conftant 
fuccefiion  of  food  excites  a new  contraction  in  the 
parts  above,  by  irritating  them,  while  no  contrac- 
tion of  the  colon  propagates  a ftimulus  backwards 
to  the  lower  part  of  the  ileum  ; hence  the  loofe  co- 
lon receives  what  defeends  into  it,  and  unloads  it- 
felf into  the  large  unactive  caecum  more  ealily,  than 
it  can  repel  upwards  the  aliments  it  has  ^ecei^'ed, 
and  which  are  refifted  by  the  preffure  of  the  inteftine 
propelling  frelh  matter.  Anatomifts  obferve,  that 
this  motion  acts  more  ftrongly  downwards  than  up- 
wards, and  that  the  fuperior  parts  of  the  inteftines 
are  more  irritable.  But  as  often  as  any  infupcrable 
cbftacle  refifts  the  paffage  of  the  aliment,  the  feat 
of  the  principal  contraction  will  be  there,  and  the 
aliment  will  be  repelled  upwards,  even  from  the 
valve  of  the  colon,  through  the  whole  length  of  the 
inteftines, into  the  ftomach,  and  laftiy  into  the  mouth 
itfelf. 

Dccxxxv.  This  periftaltic  motion,  in  which  the 
inteftine  is  conftricted,  is  performed  by  the  circular 
fibres,  which  are  capable  of  moft  exaflly  emptying 
the  tube,  fo  as  to  propel  downwards  the  moft  mi- 
nute bodies,  fucli  as  needles  or  powders.  But  the 
revolutions  of  the  inteftines,  drawn  upwards  or 
downwards,  and  the  bending  of  the  ftraight,  and 
the  ftraightening  of  the  crooked  portions,  which  are 
fo  confpicuous  in  animals,  are  pei'formed  by  the  long 
fibres,  and  which,  moreover,  when  they  contract 
themfelves  towards  the  feat  of  the  prefent,  ftiinuia- 


Chap.  XXIV,  INTESTINES.  363 

ting  food,  we  fee  dilate  the  fucceeding  portion  of 
inteftine,  and  fit  it  for  receiving.  The  fame  con- 
traftion,  forces  the  villous  membrane  into  the  cavity 
of  the  intellines,  and  renders  the  folds  longer  ; and 
exprelTes  the  mucus,  fo  that  luch  a quantity  is  ap- 
plied to  the  alimentary  mafs,  as  is  required  by  the 
irritation  and  degree  of  the  ftimulus.  They  alfo 
produce  frequent,  and  generally  harmlefs,  introfuf- 
ceptions,  by  drawing  up  the  fucceeding  portion  of 
inteftine,  againft  that  which  is  contrafted,  in  fuch 
a manner,  that  the  former  is  received  within  the 
latter,  which  is  relaxed, 

Dccxxxvi.  The  alimentary  pulp,  therefore,  dilu^ 
ted  with  the  pancreatic  juice  and  that  of  the  intef- 
tines,  intimately  mixed  with  the  faponaceous  bile, 
and  covered  with  mucus,  is  accurately  triturated, 
and  more  efticacioufty  than  in  the  ftornach,  in  pro- 
portion as  the  fides  of  the  fmall  inteftines  approach 
nearer  together,  and  to  the  length  of  the  feries  of 
the  periftaltic  motion  afling,  and  to  the  quantity 
of  animal  juices  affufed.  The  vifcid  pulp,  inter- 
mixed with  air,  becomes  frothy,  without  fermenta- 
tion, and  the  air  continues  to  have  the  fame  effects 
as  in  the  ftornach,  but  fo  that  every  acid  tendency 
within  the  inteftines  is  counterafted.  But  the  oily 
or  fat  parts  of  the  food,  diflblved  by  the  bile, 

I (dccxv.)  and  mixed  with  the  watery  juices,  ac- 
j quire  ufually  a bright  white  colour,  like  an  emul- 
1 fion,  firft  viftble  in  the  duodenum,  below  the  en- 
trance  of  the  biliary  du6t ; and  afterwards  adher- 
; irig  clofely  to  the  villous  coat,  throughout  the  whole 
' length  of  the  fmall  inteftines.  But  the  gelatinous 
! juices  of  flefti  meats,  diluted  by  copious  affufion  of 
water,  and  being  of  themfelves  of  a fubvifcid  na- 
ture,  adhere  to  the  villous  coat,  and  are  prepared  for 
i!  abforption.  The  water  and  watery  liquors  are  all 
\\  very  greedily  abforbed  by  the  veins  : and  yet  the 
[I  faeces  never  grow  thick  in  the  fmall  inteftines,  as  far 
I as  I have  obferved,  becaufe  the  water  abforbed  is 
! { repaired 

' 1 


INTESTINES. 


364 


Chap.  XXIV. 


repaired  by  the  arterial  vapour  and  the  mucus  ; nor 
do  they  becoipe  fetid  in  any  confiderabLe  degree, 
both  on  account  of  the  great  quantity  of  diluting 
juices,  and  becadfe  their  quick  progrelEon  does  not 
allow  them  time  for  putrefaction.  In  the  beginning 
of  the  jejunum,  the  white  mafs  is  coloured  with 
bile  ; in  the  end  of  the  ileum,  it  is  entirely  mu- 
cous. Thofe  remains,  which  are  more  earthy,  grofs, 
coarfe,  and  acrid,  and  were  excluded  by  the  abforb- 
ing  orifices,  either  by  their  own  weight,  or  by  fome 
power  acting  as  a fphincler,  defcend  into  the  large  j 
inteftines,  being  gradually,  forced  down,  fo  as  to 
complete  their  whole  courfe  in  the  fpace  of  about 
twenty-four  hours.  But  within  three  or  four 
hours,  or  a little  more,  almoft  all  the  chyle  is  ex- 
tracted. 

Dccxxxvn.  The  confiderable  length  of  the  fmall 
intelline,  which  is  live  times  longer  than  the  body, 
or  more,  the  great  furface  of  the  villous  membrane 
increafed  by  folds,  the  incredible  number  of  exhal- 
ing and  abforbing  veffels,  the  flow  progrefs  of  the 
food  through  the  large  inteftines,  and  the  gi’eat 
quantity  of  the  inteftinal  juice,  poured  to  the  ali- 
mentary mafs,  have  the  eflect  of  providing  abun- 
dantly, in  the  fmall  inteftines,  every  requilite  for 
diluting  the  food  with  our  juices  ; for  their  abforp- 
tion  into  the  lacfteals  and  the  mefenteric  veins  ; for 
the  abfterfton  of  vifcidities  from  the  inteftine  ; for 
preventing  adhefions  and  coagulations  : for  the  fup- 
prefllon  of  any  acidity,  not  yet  fubdued  ; and  for 
the  deftruction  of  the  deleterious  qualities  in  many 
juices,  which,  being  direcftly  mixed  uith  the  blood, 
inftantly  kill,  but  are  without  injury  received  by 
the  mouth.  Hence  the  inteftines  are  long  in  ani- 
mals that  feed  upon  any  hard  food,  but  Ihorter  in 
carnivorous  ones,  and  Ihortell  in  thofe  that  live  up- 
on juices  alone  ; and,  in  man,  an  uncommon  Ihort- 
nefs  of  the  inteftines  has  been  attended  with  hun- 
ger, and  fetid  and  fluid  fteces. 


Dccxxxvin, 


INTESTINES. 


Chap,  XXV. 


3^5 


Dccxxxviii.  The  heat,  by  which  the  aliment  is 
fomented,  and  which  is  well  fitted  for  the  folution 
of  the  gelatinous  matter,  and  for  exciting  the  be- 
ginning of  putrefaffion,  is  therefore  the  principal 
caufe  of  the  fetor,  which  is  gradually  produced  in 
the  aliment ; and  alfo  of  that  thinnefs  by  which  the 
ufeful  part  of  the  aliment  is  fitted  for  abforption. 
But  the  air  alfo,  inclofed  in  the  vifdd  aliment,  ope- 
rates, as  in  the  ftomach,  by  breaking  the  cohefion 
of  the  aliments,  if  any  yet  remain  entire.  The  in- 
teftinal  water  dilutes  the  mafles  of  aliment ; and  if 
any  hard  part  remains,  foftens  it  by  maceration. 
The  bile  being  intimately  mixed  with  oil,  diflblves 
it,  and  renders  it  mifcible  with  water. 


CHAP.  XXV. 

LARGE  INTESTINES. 

Dccxxxix.  "T'TTHAT  remains,  after  the  chyle 
V V been  abftraded,  confifts  of 
fome  portion  of  the  bile,  but  mucous  and  degene- 
rate ; fome  part  of  the  human  mucilage  ; mofl;  of 
the  earthy  parts  that  were  in  the  food  5 all  thofe 
parts,  which  by  their  acrimony  were  rejeded  by 
the  abforbing  mouths,  changed,  however,  by  putre- 
faction, (dccxxxvi.)  with  all  the  folid  fibres  and 
membranes,  which  refilled  the  powers  of  macera<< 
tion  and  the  periftaltic  motion. 

DccxL.  All  thefe  remains  pafs  from  the  extrem- 
ity of  the  ileum  into  the  caecum,  in  which  they 
ftagnate  ; namely,  the  extremity  of  the  fmall  in- 
teftine  applies  itfelf  obliquely  to  the  right  fide  of 
the  colon,  refting  upon  the  right  ileum  and  iliac 
-mufcle,  fo  that,  upon  the  whole,  it  afcends,  but 
more  with  its  lower  fide,  and  lefs  with  its  upper^ 
which  is  aim  oft  tranfverfe.  But  the  extremity  of 


INTESTINES. 


Chap.  XXV. 


^66 

the  nervous  and  villous  coats,  and  tranfverfe  flefliy 
fibres  of  the  ileum,  are  fo  extended  betwixt  the 
departing  flefhy  fibres  and  nervous  coat  of  the  co- 
lon, that  there  hangs  within  the  cavity  of  this 
large  intelline,  a moveable,  foft,  double  prelecting 
fold,  compofed  of  the  villous  and  nervous  coats  of 
the  large  inteftine,  and  of  the  villous  and  nervous 
coats  of  the  fmall  inteftine,  and  of  the  interpofed 
fleftiy  fibres  of  the  ileum  and  colon,  connected  by 
much  cellular  fubftance.  The  upper  fold  is  tranf- 
verfe and  fhorter,  the  low'-er  is  larger,  longer,  and 
afeending.  They  are  conjoined  by  a fmall  pro- 
dudtian  of  the  fame  kind,  more  efpedally  where 
they  approach  in  the  right  fide.  Betwixt  thefe 
two  folds,  the  mouth  of  the  ileum  opens,  like  a 
tranfverfe  flit.  By  inflation,  this  ftructure  is  much 
altered,  afl’uming  the  appearance  of  membranes  and 
hard  valves.  After  the  cellular  fubftance  is  en- 
tirely removed,  and  the  interpofed  flefhy  fibres  are 
cut,  the  ileum,  Comes  out  from  the  colon,  and  the 
valvular  appearance  difappears  ; but  if  a large  part 
of  it  only  be  removed,  fo  that  it  ftill  remoins  infert- 
ed  by  fome,  it  refembles  a fphincler. 

DccxLi.  Below  the  entrance  of  the  ileum,  at  the 
diftance  of  fome  inches,  the  great  inteftine  defeends 
and  refts  with  an  impervious  extremity,  upon  the 
ileum.  From  the  lower  part  of  this,  towards  the 
light  fide,  a very  acutely  conical  fmall  inteftine 
extends,  in  adults  flender,  in  the  foetus  proportion- 
ally larger,  varioufly  incurvated  upwards,  fome- 
times  downwards,  and  full  of  fmall  mucous  glands,- 
which  pour  out  a glutinous  matter  to  the  frees  ; 
in  the  foetus,  the  colon  itfelf  is  continued  wdth  a 
conical  termination  into  the  appendix.  But  the 
weight  of  the  fuperincumbent  fcybalse,  deprefllng 
the  fpaoe  on  the  right  fide  of  the  appendix ; the 
ftrength  of  the  cellular  texture  uniting  the  left 
part  of  the  caecum  with  the  ileum  ; the  ftrength  of 
the  flcfliy  fibres  uniting  both  inteftines ; the  very 

contractile 


Chap.  XXV. 


INTESTINES. 


3^7 

contracHle  force  of  the  ligaments ; the  fitnefs  of 
the  anterior  fac  of  the  oecum,  for  eafily  receiving 
the  faeces  fi'om  the  ileum  5 all  contribute  to  remove 
the  appendix  from  the  middle,  fo  that  it  arifes  from 
the  left  lide  of  the  extremity  of  the  colon  : and  to 
form  the  thick  and  pendulous  bag  of  the  colon 
lying  fartheft  to  the  right  fide,  and  which  is  pecu- 
liar to  adults.  When,  therefore,  the  remains  of  the 
alimentary  mafs  come  from  the  ileum  into  the 
colon,  they  fall  by  their  weight  into  this  impervi- 
ous bag,  and  ftagnate  there,  and  become  putrid^ 
both  from  the  warmth  of  the  place  and  their  own 
nature ; and  here,  efpecially,  the  fetor  of  the  ex- 
crements begins. 

DccxLii.  The  inteftine  which  is  continuous  with 
the  caecum,  and  indeed  the  fame,  is  named  the  co- 
lon. This  thick  and  very  large  inteftine,  which  is 
much  ftronger  than  the  fmali  inteftines,  begins  in 
the  right  ileum,  (dccxl.)  afcends  along  the  kid- 
ney, lies  in  the  angle  of  the  right  hypochondriuna 
under  the  liver,  and  is  connedred  to  both  vifcera 
by  the  peritonaeum.  Then  it  paffes  under  the  liver 
and  ftomach,  for  the  moft  part  tranfverfely,  to  the 
fpleen,  under  which  it  lies,  (dclxxvi.)  and  in  a 
deep  recefs  under  the  left  ribs,  it  is  often  reflected 
upon  itfelf.  Then  it  defcends  again,  and  having 
made  a large  flexure  to  the  left  ileum,  (ncnviii.)  it 
is  continued  with  the  lower  part  of  this  flexure  in- 
to the  pelvis,  and  becomes  the  reftum. 

DccxLiii.  The  ftructure  is,  on  the  whole,  the 
fame  with  that  of  the  fmali  inteftines,  but  it  differs 
in  feveral  particulars.  And  firft,  all  the  longitudi- 
nal fibres  are  collected  into  three  bundles,  which 
run  through  the  whole  extent  of  the  inteftine ; 
and  of  thefe  one,  and  that  the  largeft,  lies  naked  j 
another,  at  its  origin,  is  concealed  by  the  omentum, 
and  the  third  by  the  mefocolon.  Thefe  are  fliorter 
than  the  inteftine,  and  contradt  it  fo  that  the  ner- 
vous and  villous  membranes  (dcxliv.)  projeft  in- 
wardly. 


INTESTINES. 


Chap.  XXV. 


368 

wardly.  Thefe  fibres  are  connected  mofl  accurately 
with  the  external  coat  of  the  inteftine  ; but  in  tlie 
intermediate  places,  and  chiefly  at  the  mefocolon, 
is  feated  the  firft  cellular  coat  replenifhed  with  fat. 
Being  dilated  at  their  origin,  they  adhere  to  the 
vermiform  appendix.  In  the  extremity  of  the  co- 
lon, there  are  often  only  two  ligaments,  the  two 
fmaller  joining  into  one.  They  diffufe  themfelves 
upon  the  rectum  fo  as  to  cover  it  entirely. 

DccxLiv;  Again,  the  flefhy  and  nervous  coat, 
third  cellular  and  villous  tunics  of  the  colon,  are 
extended  into  much  larger  wrinkles  in  the  parts 
betwixt  the  ligaments,  often  projecting  in  a three- 
fold rank,  which  being  fuftained  by  the  ligaments, 
are  able  to  fupport  a little  the  fcybalae,  and  refift 
their  relapfe.  In  the  beginning  of  the  colon,  they 
are  very  exactly  threefold  ; but  in  its  progrefs,  they 
vary  more  and  more,  being  lefs,  and  double,  and 
folitary,  and  fmall  and  large  intermixed,  and  entire- 
ly abfent.  Where  the  ligaments  which  contrad:  tha 
colon,  difappear,  thefe  valves  difappear  almoft  en- 
tirely. Laftly,  the  villous  coat  is  thinner,  and 
vnthout  villi,  but  wrinkled  and  porous,  furnifhed 
both  with  large  pores  leading  to  proper,  large, 
round,  folitary  follicles,  and  with  innumerable 
fmall  pores  leading  to  fmaller  follicles.  Both  kinds 
fupply  a great  quantity  of  mucus. 

Dccxi-v.  The  blood-veffels  of  the  large  inteftines 
are  partly  from  the  greater  and  left  mefenterics, 
and  partly  from  the  hypogaftrics.  The  middle 
colic  artery  arifes  from  the  large  mefenteric  trunk, 
as  that  defcends  behind  the  tranfverfe  mefocolon.  It 
rifes  upwards  with  one,  two,  and  fometimes  three 
branches  to  the  tranfverfe  mefocolon,  and  unites 
on  the  right  fldc  with  the  ileo-colic  ; and  on  the 
left,  with  the  lower  mefenteric,  in  a very  large 
arch,  which  ir  the  largeft  of  all  the  arterial  inofcu- 
lations  in  the  numan  bodyn  Again,  under  the  me- 
focolon, from  the  fame  large  mefenteric  artery,  a 

larger 


Chap.  XXV. 


INTESTINES. 


3^9 

larger  branch  goes  dire6lly  to  the  valve  of  the  ile- 
um with  the  colon,  and  inofculates  upwards  at  the 
right  of  the  colon  with  the  middle  colic  ; and  to  the 
left  with  the  mefenteric  ; but  from  the  middle  of 
the  mefentery  it  gives  a branch  that  runs  along  the 
mefocolon  of  the  appendix  verraiformis,  and  ter- 
minates with  two  branches  in  the  two  folds  of  the 
ileum  and  colon,  both  the  anterior  and  pofterior. 
Laltly,  the  lower  mefenteric,  arifes  by  its  proper 
trunk  from  the  aorta,  betwixt  its  bifurcation  and 
the  renal  arteries,  and  goes  to  the  left  part  of  the 
colon  : upwards  it  forms  a large  arch,  with  the 
middle  colic  j downwards  in  three  or  four  trunks, 
it  fpreads  over  the  iliac  flexure  of  the  colon,  and 
defcends  even  into  the  rectum.  There  tire  reftum 
receives  various  branches  from  the  middle  hemor- 
rhoidal, ariling  from  the  laft  trunk  of  the  hypo- 
gaftricsj  and  conjoined  with  the  former.  The  ul- 
timate arteries  are  from  the  fame  trunk,  but  arife 
without  the  pelvis.  I pafs  over  the  fmaller  colics, 
ariling  from  the  fpermatics,  intercoftal,  omental, 
capfulary,  and  lumbar  arteries.  The  veins,  like  the 
arteries,  run  together  into  the  gaftrocolic,  and  the 
internal  hemorrhoidal,  and  thence  into  the  vena 
oortarum  : and  into  the  middle  and  external  he- 
morrhoidals,  and  the  trunks  of  the  iliacs. 

DccxLvi.  The  divilion  of  the  veflels  to  the  large 
inteftines,  differs  much  front  that  of  the  fmall  in- 
teftines.  Their  arches  are  lefs  frequent  and  lefs  of- 
ten fubdivided ; the  trunks  follow  the  courfe  of  the 
inteftines  a long  way  ; the  glands  feated  on  them 
are  fewer  ; the  branches  on  the  inteftines  lefs  ar- 
bufcular,  divided  at  lefs  angles,  and  more  tortuous  ; 
and  the  reticulation  in  the  cellular  fubftance  is 
loofer.  An  exhaling  moifture  diftils  into  the  cavi- 
ty of  the  inteftines,  and  the  veins  likewife  abforb  a 
thin  fetid  vapour  from  the  faeces.  The  external, 
and  perhaps  alfo  the  internal  veins,  fwelling  into 
varices,  pour  out  the  hemorrhoidal  blood  j which 
A a is 


INTESTINES. 


Chap.  XXV. 


is  always  unnatural,  although  fometlmes  infracHons 
of  the  veffels  of  the  porta  are  relieved  by  that  eva- 
cuation. 

DccxLvii.  But  there  are  alfo  lymphatic  veffels, 
arifing  from  the  whole  tract  of  the  colon,  and  from 
the  rectum,  which  unite  with  thofe  of  the  loins. 
We  are  not  without  examples  of  chyle  having  been 
found  inftead  of  lymph,  in  thefe  lymphatics,  arifing 
from  the  colon  ; a proof,  that  even  in  this  place 
fomething  ftill  remains,  which  may  be  added  to  the 
blood  with  advantage. 

DccxLviii,  The  nerves  proceed  from  the  left  co- 
lic plexus  compofed  by  the  defeending  branches  of 
each  renal  plexus,  and  others  arifing  from  the  in- 
tercoftal  trunk  in  the  thorax  and  loins,  and  others 
from  the  large  mefenteric  plexus.  Thefe  accom- 
pany the  lower  mefenteric  artery,  and  go  to  the  co- 
lon. The  lowermoft  nerves  arife  from  the  plexus 
juft  mentioned,  and  go  to  the  rectum,  vithin  the 
pelvis  others  go  to  the  fame  inteftine  from  the  low- 
er intercoflals,  and  from  the  nerves  of  the  facrum. 
Thefe  nerves  are  not  numerous,  and  the  inteftine  is 
not  very  fenfible,  that  it  may  endure  the  hard  and 
acrid  faeces.- 

Dccxnix.  Tlie  inteftinal  faeces,  therefore,  retain- 
ed in  the  blind  beginning  of  the  large  inteftines, 
(dccxl.)  become  dry  by  the  abforption  of  their 
fluid  parts,  fliaped  by  the  round  and  contracted  co- 
lon, afeend  from  the  bottom  of  the  caecum,  being 
elevated  by  the  long  ligaments,  which  unite  in  the 
v'orm  like  appendix.  And  here  the  manner  in 
w'hich  the  faeces  are  propelled  by  the  contraction  of 
the  circular  fibres,  appears  better  than  in  the  fmall 
inteftines.  The  longitudinal  fibres  being  drawn  to- 
wards the  contracted  portion  of  the  inteftine,  as  to  • 
a fixed  point,  draw  the  lower  part  of  the  inteftine 
upwards,  and  dilate  it ; then  the  next  part  of  the 
inteftine,  to  which  the  faeces  are  brought,  being 
irritated  in  like  manner,  contracts  the  long  fibres 

toward? 


Chap.  XXV. 


INTESTINES. 


37^ 

towards  it  ; by  a fiiccellive  repetition  of  which 
adion,  the  faeces  finifli  their  courfe  through  the 
whole  large  inteftine  j for  the  moft  part  within 
twenty-four  hours  in  a healthy  perfon.  For  this 
periftaltic  motion  of  the  large  inteftines  may  be  feen 
in  living  animalsj  and  in  the  human  body  from 
wounds  ; it  is  alfo  confirmed  by  the  antiperiflaltic 
motion,  and  by  the  phenomenon  of  giyfters  being 
difcharged  through  the  mouth.  The  fame  fibres 
refill  the  air  contained  in  the  inteftines ; and  flatu- 
lence is  faid  to  be  generated  as  often  as  they  are 
overcome  and  yieidj  and  the  inteftine  is  dilated. 

DCCL.  While  the  grofs  faeces  afcendfrom  the  cae- 
cum along  the  folds  (dccxl.)  or  valves,  at  the  en- 
trance of  the  ileum,  they  incline  the  lower  fold  to 
the  left,  and  backwards,  and  draw  down  the  liga- 
ment common  to  both  valves,  and  thus  deprefs  the 
upper  fold  downwards  : thus  the  paflage  is  accurate- 
ly Ihut,  fo  that  nothing  may  return  info  the  ileum  ; 
which,  however,  cannot  be  done  fo  accurately  in  a 
fluid  ftate  of  the  faeces.  The  faeces,  when  falling 
down  from  the  upper  parts,  deprefs  the  upper  valve, 
and  thus  accurately  exclude  themfelves.  This  hap- 
pens very  exacftly  with  hardened  faeces,  but  not  fo 
accurately  with  fluid  fasces.  From  thence,  becoming 
more  and  more  dry  and  figured,  they  continue  to 
move  flowly  forwards  by  the  fame  caufes  (dccxlix.) 
through  the  whole  colon,  which  is  repeatedly  bent, 
and  of  five  or  feven  feet  in  length,  in  fuch  a fpace 
of  time  as  is  fufficient  to  give  no  interruption  to 
the  affairs  of  human  life  ; and  which  is  lefs  than 
twenty-four  hours,  by  the  time  the  alimentary  mafs 
remained  in  the  fmall  inteftines. 

DccLi.  At  length  the  hardened  excrement  falls 
into  the  return,  which  is  at  firft  inclined  down- 
wards, and  then  alfo  forwards,  of  a broad  and  flat 
figure,  at  firft  contiguous  to,  and  afterwards  fpread 
under  the  bladder,  or  vagina,  but  connedted  more 
with  the  latter  than  with  the  former.  Here  the  fsecej 
A a 3 are 


INTESTINES. 


Chap.  XXV. 


37^ 

are  colleclcd  for  a great  while,  and  often  to  a great 
quantity,  being  a part  which  is  loofe,  or  furround- 
cd  with  foft  vifcera  and  mufcles,  and  much  fat. 

DccLii.  The  ftrufture  of  the  reclum  differs  very 
much  from  that  of  the  other  inteftines.  The  ex- 
ternal membrane  or  peritonseum  covers  it  only  be- 
fore, while  behind  it  is  connected  to  the  region  of 
the  os  facrum,  by  a very  broad  ftratum  of  cellu- 
lar fubftance,  replenilhed  with  fat,  and  many  con- 
globate glands.  The  rnufcular  fibres  are  much 
itronger  than  in  the  other  inteftines,  efpecially  the 
longitudinal  ones,  wEich  being  compofed  of  the 
three  ligaments,  expanded  and  feparated,  firft  oc- 
cupy the  anterior  face,  and  then  the  w'hole  intef- 
tine  : they  dilate  it  againft  the  advancing  faeces, 
and  draw  it  back  after  tliey  are  excluded.  But  the 
tranfverfc  fibres  are  alfo  ftrong,  and  their  laft  oval, 
tumid  ring,  is  the  internal  fphincler  by  which  the 
opening  of  the  anus  is  accurately  clofed. 

DCCLiii.  Moreover,  the  villous  tunic,  wiiich  is 
extremely  full  of  pores,  and  rough  with  polygonous 
and  tender  wrinkles,  has  likewife  fome  finufes  pe- 
culiar to  itfelf.  Namely,  the  part  of  the  inteftine 
next  to  the  fkin  and  inferior  orifice,  forms  a white 
firm  valvular  circle,  into  >vhich  defcend  longitudinal 
folds,  but  incurvated  and  approacliing  to  each  oth- 
er on  the  circle  itfelf.  Betwixt  thofe  folds,  there- 
fore, finufes  are  interpofed,  hollow  upw^ards,  and 
of  a greater  depth  towurds^the  bottom.  Into  their 
cavities  open  mouths  from  large  m.ucous  glands  ; 
while  the  mara.in  of  the  anus  itfelf  is  defended  bv 

O , * 

febaceous  glands,  that  it  may  not  be  excoriated  by 
the  hard  and  acrid  faeces. 

DcciJv.  There  are  allb  proper  mufcles  which 
govern  the  anus.  The  external  fphincler  is  broad 
and  ftefhy,  and  confifts  of  tw'O  plates  of  femi-elliptic 
fibres,  which  crofs  each  other  towards  the  cocc)  X, 
and  towTii'ds  the  genital  parts.  And,  in  the  form- 
er place,  thev  are  inferted  by  fleflay  bundles  into  a 

callous 


Chap.  XXV. 


INTESTINES. 


373 

Cculous  cellular  fabric  defcending  from  the  coccyx. 
In  the  latter,  in  like  manner,  they  are  attached  by 
fimiiar  bundles  to  the  fkin  of  the  perinaeum  ; but 
by  three  ftronger  than  the  others,  one  middle,  and 
two  lateral  into  the  accelerator  and  bulb  of  the  ure- 
thra, the  lateral  ones  partaking  both  of  the  nature 
of  a fphincter  and  levator.  The  fibres,  therefore, 
of  the  fphinfter,  approaching  to  a ftraight  line  be- 
tween their  anterior  and  pofterior  fixed  extremities, 
clofe  the  opening  of  the  anus,  which  lies  between 
them.  With  the  internal  fphincler,  the  external 
one  is  conjoined  by  a liefhy  portion,  that  they  may 
operate  together.  Their  affion  is  voluntary  and 
not  perpetual ; for  the  anus  feems  to  be  clofed  nat- 
urally, by  the  narrownefs  of  its  orifice,  compared 
with  the  largenefs  of  the  inteftine,  by  the  wrinkles 
correfponding  to  the  other  (dccliii.)  by  the  ftrength 
of  the  tranfverfe  fibres  of  the  internal  fphincler,  and 
by  the  incumbent  bladder. 

DCCLV.  But  the  office  of  the  levators  is  different. 
They  are  large  and  complicated  mufcles.  They 
defcend  betwixt  the  oppofite  ofl'a  ifchia,  are  placed 
under  the  reclum  and  bladder,  and  fullain  both, 
and  prevent  the  reclum  from  defcending  and  gap- 
ing difgullingly.  Moreover,  by  their  fibres  fpread- 
ing  extenfively  in  the  manner  of  a fphincler,  and 
being  joined  to  that  mufcle,  they  can  dilate  its  fibres, 
and  open  the  anus  ; but,  at  the  fame  time,  they  el- 
evate and  fullain  the  inteftine  from  prolapfing  wJrile 
the  fteces  are  palling.  They  arife,  as  is  weft  known, 
from  the  fpine  of  the  ifchium,  os  ileum,  and  fyn- 
chondrolis  of  the  offa  pubis,  terminating  the  mar- 
gin of  the  great  foramen  of  the  pubes,  and  from 
that  part  of  the  ifchium,  wffiich  is  above  the  tuber- 
cle. Finally,  they  meet  together  under  the  coc- 
cyx, into  which  they  are  inferted  by  numerous  fi- 
bres. 

DccLvi.  Therefore,  whenever  the  fteces  are  col- 
Icftcd  \vithin  the  reftum  in  any  great  quantity, 

and 


CHYLIFEROUS  Chap.  XXV.- 


374 

and  become  troublefome  by  the  irritation  of  their 
weight,  or  acrimony,  even  to  the  adjacent  vifcera  ; 
they  are  forced  by  the  power  of  the  will  through 
the  llraits  of  the  coUapfed  inteftine  (dccliw)  by 
the  force  of  the  incumbent  diaphragm,  exerting  an 
effort ; which  being  drawn  downwards  with  great 
force,  preffes  downwards  the  vifcera  of  the  abdo- 
men, which  arc  alfo  refifted  by  the  contraction  of 
the  abdominal  mufcles,  and  forces  the  contents  of 
the  bladder  or  reclum  through  the  inferior  opening 
between  the  bones  of  the  pelvis,  where  the  refin- 
ance is  leaft.  When  the  refiflance  of  the  anus  is 
thus  overcome,  the  force  of  the  diaphragm  abates, 
and  the  fgeces  are  difeharged  from  the  body,  by  the 
periftaltic  motion  of  the  inteftine  itfclf.  After  the 
ibsces  are  expelled,  the  inteftine  is  drawn  back  by 
its  longitudinal  fibres  ; and  the  anus  being  con- 
tracted by  both  its  fphinclers,  fliuts  its  orifice  as 
before. 

DCCLvii.  Thefe  faeces  in  man,  and  carnivorous 
animals,  are  very  fetid,  almoft:  putrid,  fubalkaline, 
foft,  and  contain  much  oil  mixed  with  faiine  mat-, 
ter,  which  are  the  remains  both  of  the  aliments  and 
of  the  bile  and  other  humours  of  the  human  body. 
An  acrid  and  fetid  water  returns  from  the  faeces 
into  the  blood  ; hence,  coflivenefs  in  fevers  is  hurt? 
ful,  as  by  its  addition  it  promotes  putrefcency. 


CHAP.  XXV.* 

CHYLIFEROUS  VESSELS. 

uccLvili.  ^ S HE  chyle  is  a white  juice  (dccxxxvi.) 

§ extracted  from  the  aliments,  which 
is  poured  into  the  blood.  It  feems  to  be  compofed 
of  water  and  oil,  as  appears  from  its  tafte,  being 
fweet  with  fome  mixture  of  faltnefs,  from  its  acci- 

cent 


Chap.  XXV.* 


VESSELS. 


375 

cent  nature,  from  the  whitenefs  of  its  colour, 
from  its  fpontaneous  reparation  and  coagulabili- 
ty, and  from  its  lightnefs,  by  which  it  fwims  on 
the  blood : in  all  which  properties  it  very  much 
refembles  an  emulfion.  It  is  compofed  of  vege- 
table farina,  with  lymph  and  animal  oil.  It  every 
where  retains  the  properties  of  the  volatile  and  oily 
aliments.  It  changes  into  milk  with  very  little  al- 
teration. But  then,  the  glutinous  pellucid  ferum 
which  it  contains,  becomes  more  manlfeft,  being 
coagulable  into  a kind  of  a jelly,  by  expofure  to  a 
high  temperature,  or  by  evaporating  its  water. 

DccLix.  That  the  chyle  is  abforbed  into  the 
lacteal  veflels  from  the  villous  coat  of  the  inteftines, 
to  which  it  adheres,  has  been  long  known,  by  ex- 
periments with  coloured  liquids,  which  defcribed 
the  fame  courfe  ; from  the  hmilitude  of  the  white 
liquor,  as  feen  in  the  lacteals,  and  out  of  them  and 
from  the  venous  nature  of  ladleal  veifels.  But  late 
experiments  have  given  us  better  information  on 
many  particulars.  The  chyle  is  abforbed  by  the 
patulent  orifice  in  the  extremity  of  each  of  the  villi, 
by  a force  fimilar  to  that  of  capillary  tubes  ; is  re- 
ceived into  the  hollow  villi,  which  are  relaxed 
when  the  inteftine  kfeif  is  relaxed  5 but  the  veficle, 
being  compreffed  by  the  fucceeding  confiriftion  of 
the  mufcular  fibres  of  the  inteftine,  the  chyle  k 
preiTed  on  into  the  du(ft,  which  begins  to  appear 
in  the  fecond  cellular  ftratum.  But  there  is  a dou- 
ble feries  of  thefe  trunks,  one  anterior,  the  other 
pofterior,  as  we  obferved  of  the  blood-veft’els, 
(dccxxix.)  From  thence  the  lafteal  veflel,  already 
united  into  a larger  canal,  pafles  into  the  firft  cel- 
lular ftratum,  and,  in  general,  follows  the  courfe  of 
the  arteries,  and  likewife  accompanies  their  arches, 
being  conjoined  with  others  of  the  fame  kind  into 
a very  obliquely  angled  netv/ork.  This  kind  of 
vefTels  hitherto  has  been  obferved  only  in  quadru- 
peds, In  the  large  inteftine  they  arife  without  the 

veficle. 


CHYLIFEROUS 


Chap.  XXV.* 


376 

veficle.  Very  many  arife  from  tlie  firft  part  of  the 
fmall  inteftines  under  the  mefocolon  ; fome  from 
the  duodenum,  and  a few  from  the  large  inteftines 
themfelves. 

Dcci-x.  The  lacteal  veffels  are  valvular  in  the 
very  firft  cellular  texture  of  the  inteftine,  being 
provided,  like  the  lymphatics,  with  very  frequent, 
double,  lunated  valves,  (lvii.)  which  admit  the 
chyle  paffing  from  the  inteftines  but  prevent  its  re- 
turn. Through  this  whole  courfe,  the  chyle  is 
propelled  by  the  periftaltic  motion  of  the  inteftines; 
by  the  periftaltic  aftiion  of  the  velTels  themfelves, 
which  are  certainly  irritable,  even  after  death  pro- 
pelling the  chyle  ; and  by  the  confiderable  prelture 
of  the  abdominal  mufcles,  directed  by  the  valves. 

DCCLXi.  But  betvixt  the  plates  of  the  mefentery, 
at  the  divifions  of  the  veftels,  are  found  an  infinite 
number  of  glands,  of  the  conglobate  kind,  but  fofter 
and  fpongy,  conlifting  of  cellular  texture  full  of 
juices,  covered  with  an  external  membrane,  lefs 
hard  than  in  other  parts,  and  variegated  with  num- 
berlcfs  fmall  biood-vefiels.  Some  lacteal  veftels  feem 
to  pafs  by  thefe  glands  : the  greateft  number  enter 
them  ; and,  being  divided  and  fubdivided  through 
their  cellular  fabric,  compofe  the  greateft  part  of 
the  gland.  On  the  other  hand,  other  lacteal  veftels 
originate  in  every  gland  ; and,  being  mutually  join- 
ed, compofe  trunks,  of  which  the  ultimate  and 
iargeft  go  out  from  tlie  gland.  In  the  fame  man- 
ner the  chyle  enters  two,  three,  or  four  glands,  in 
fticceftlon  ; nor  does  any  laefteal  veflel  arrive  at  the 
thoracic  duff  without  entering  fome  of  thefe  glands, 
although  it  may  occafionally  pafs  by  fome  without 
entering  them.  That  tliis  is  the  true  courfe  of  the 
chyle,  and  that  it  paftes  from  the  inteftines  to  the 
mefenteric  glands,  appears  from  tying  them,  by  the 
veftels  growing  turgid  betwixt  the  ligature  and  the 
jmeftine  ; from  fchirrofities  in  the  glands,  by  which 
they  are  rendered  confpicuous  , and  from  the  na- 
ture 


VESSELS. 


CiAp.  XXV.* 


3J  / 


ture  of  the  valves  preventing  any  return  to  the  in- 
teftines. 

DCCLXii.  What  happens  to  the  chyle  in  thefe 
cellular  I'paces  is  not  fufficiently  known  ; but  it  ap- 
pears that  fome  thin  liquor  is  fecreted  from  the  ar- 
teries in  thefe  glands,  by  the  aftufion  of  w'hich  the 
chyle  is  diluted.  For  it  is  obferved,  that  after  the 
chyle  has  paffed  all  the  glands,  it  appears  more  wa- 
tery ; and  thin  liquors,  injecled  through  the  arte- 
ries, exude  into  the  cells  of  the  glands,  and  mix 
with  the  chyle,  lince  the  laftcal  vcflels  may  be  filled 
through  the  arteries.  Laftly,  this  milky  fluid  ap- 
pears manifeftly  in  the  glands  of  infants. 

DccLxin.  From  the  laft  glands,  which  are  col- 
lected together  in  the  centre  of  the  mefentery,  a 
few  very  large  lacteal  veflels  go  out,  to  the  number 
of  four,  five,  or  more,  which  afcend  with  the  me- 
fenteric  artery,  and  intermix  with  the  lymphatic 
plexus,  which  arifing  from  the  lower  parts  of  the 
body,  creeps  over  the  renal  vein,  and  afterwards 
with  that  which  comes  behind  the  aorta  from  the 
lumbar  glands,  and  with  the  hepatic.  A duft  is 
thus  produced,  fubject  to  great  varieties,  but  which 
niofl:  frequently  expands  into  a veficle  of  conlider- 
able  breadth  at  the  fide  of  the  aorta,  lying  between 
that  and  the  right  appendix  of  the  diaphragm,  two 
or  more  inches  long  ; and  mofi:  commonly  contin- 
ued above  the  diaphragm  into  the  thorax,  coni- 
cal both  ways  : it  is  called  the  receptacle  of  the 
chyle.  In  this  the  gelatinous  lymph  of  the  iimbs, 
and  of  the  abdomen,  mixes  with  the  chyle,  and 
dilutes  its  white  colour  ; fo  that  fometimes  it  ap- 
pears filled  with  a pellucid  or  reddifli  humour, 
but  frequently  alfo  with  a w'hite  milk.  But  there 
are  fome  inftances  where  there  are  two  or  three 
fmall  and  narrow  duels,  inftead  of  this  recep- 
tacle. This,  how'ever,  is  moft  frequent,  and  being 
comprefled  by  the  diaphragm  and  aorta,  propels 
the  chyle  with  greater  velocity,  in  proportion 

as 


378  ' CHYLIFEROUS  Chap. 

as  its  caliber  is  larger  than  that  of  the  duel  jnto 
which  it  empties  itfelf.  This  receptacle  is  rarely 
fo  fhort,  that  it  may  be  compared  with  an  egg ; but 
for  the  moft  part  it  is  broadeft  in  the  middle,  and 
decreafes  conically  towards  each  end. 

DCCLxiv.  That  the  chyle  comes  from  the  intef- 
tines  into  this  duel,  is  fliewn  from  injeclions,  by 
which  quickfilver  has  fometimes  been  puflied  from 
the  firft  lacleal  veffels  into  the  thoracic  duel ; from 
ligatures  made  on  the  duel  itfelf,  or  the  red  veins 
which  receive  it,  by  which  the  firft  and  fecond 
la<fteal  veffels  fwell ; and  from  the  manifecl  flux  of 
the  chyle  into  the  thoracic  du<ft  when  the  ligatures 
are  removed. 

DCCLXv.  The  thoracic  du<ft,  as  it  is  called  from 
its  courfe,  is  generally  Angle  ; or,  if  double  for  fome 
part  of  its  courfe,  it  foon  unites  into  one,  which 
afeends  in  a waving  courfe  behind  the  pleura,  be- 
twixt the  vena  azygos  and  the  aorta ; and  receives 
in  its  way  the  lymphatic  veffels  of  the  ftomach, 
cefophagus,  and  lungs,  palling  through  the  conglo- 
bate glands,  of  which  there  are  many  incumbent  on 
it,  and  coUecled  into  large  bunches.  It  is,  on  the 
whole,  cylindrical  ; and  often  forms  iflands,  by 
fplitting  and  uniting  again,  more  efpecially  in  its 
upper  part.  It  has  few  valves,  and  thofe  lefs  con- 
fpicuous.  About  the  fifth  vertebra  of  the  back,  it 
generally  goes  to  the  left,  behind  the  cefophagus, 
and  then  afeends  along  the  left  fide  of  the  thorax, 
behind  the  fubclavian  veffels,  till  it  arrives  near  the 
lixth  vertebra  of  the  neck. 

DCCLXvi.  Then,  being  refleded  and  often  didd- 
ed,  it  defeends  with  each  branch  dilated  into  a fort 
of  veficle,  and  enters,  either  \sdth  diftincl  or  united 
openings,  into  the  junction  of  the  fubclavian  and 
internal  jugular  vein,  by  an  oblique  courfe  from  the 
upper,  pofterior,  and  right  fide,  downwards,  to  the 
left,  and  forwards  ; or  going  on  v.ath  one  or  other 
branch,  it  enters  the  fubclavian,  on  the  outiide  of 

that 


Chap.  XXV.* 


VESSELS. 


373 

that  junftion.  It  is  guarded  by  a true,  moveable, 
and  almoft  circular  valve  ; alfo  by  its  defcent  the 
blood  is  prevented  from  entering  it.  It  is  rarely 
otherwife  difpofed  ; and  very  rarely  fplit  into  two, 
with  one  branch  entering  each  fubclavian  ; and 
yet  more  rarely  does  it  fend  a branch  into  the  vena 
azygos.  Near  its  infertion  it  receives  a large  lym- 
phatic veffel,  coming  tranfverfely  from  the  arm  ; 
and  another  defcending  from  the  head,  in  one  or 
more  trunks. 

DccLXvii.  It  appears  that  the  chyle  flows  through 
the  thoracic  duct  into  the  blood  ; becaufe,  on  tying 
the  red  veins,  both  the  thoracic  duct  and  lafteal 
veflels  which  are  inferted  into  it  fwell. 

DCCLxviii.  I have  attributed  the  firft  caufe  of 
motion  in  the  chyle,  and  of  its  abforption,  to  the 
attradion  of  the  capillary  veflels,  alternated  with 
the  periftaltic  contraction  of  the  inteftines.  The 
attraction  fills  the  villi ; the  periftaltic  force  emp- 
ties them,  and  moves  the  chyle  farther  forwards. 
The  reft  of  its  motion  feems  to  depend  on  the  force 
of  the  membrane  of  the  lacteal  veflel  itfelf,  v/hich, 
even  after  death,  expels  the  chyle,  fo  that  the  veflels 
become  pellucid,  which  before  were  milky.  The 
alternate  ccmprefling  force  of  the  diaphragm  alfo 
has  fome  efleft  ; and  the  motion  of  the  chyle 
through  the  thorax  is  fomewhat  accelerated  by  the 
receptacle,  which,  being  comprefled,  propels  the 
chyle  fo  much  the  more  quickly,  as  it  is  larger  than 
the  thoracic  du<ft. 

DccLxix.  The  chyle,  mixed  with  the  blood,  does 
not  immediately  change  its  nature  ; as  is  proved 
from  the  milk  produced  from  it.  But  five  hours  or 
more  after  a meal,  almoft  to  twelve,  during  ail 
which  time  a woman  can  afford  milk  j having  cir- 
culated near  80,000  times  through  the  body,  fo- 
mented with  the  heat  of  the  body,  and  mixed  with 
the  animal  juices,  it  is  changed,  fo  that  its  fat  feems 
to  be  partly  depofited  in  the  cellular  fubftance, 

partly 

( 


KIDNEYS. 


Chap.  XKV!. 


280 

partly  figured  into  the  red  globules,  (cxlvii.)  the 
gelatinous  part  changes  into  the  feruni  of  the  blood  ; 
and  the  watery  parts  go  off,  partly  by  urine  and 
perfpiration,  and  in  part  dilute  the  blood.  Nor  is 
it  uncommon  for  a pellucid  liquor  to  be  in  place  of 
the  chyle  in  the  lacteals  in  a dying  animal,  or  for  a 
white  liquor  to  be  in  one  part  of  the  mefentery,  and 
limpid  liquor  in  another,  in  veffels  which  perfectly 
agree  in  their  fabric.  There  are  not,  therefore,  two 
kinds  of  veffels  from  the  inteflines  ; of  which  the 
one  carries  chyle  only,  and  the  other  lymph. 

DCCLXX.  When  digeftion  is  not  going  on,  the 
lacteal  veffels  abforb  water  from  the  inteflines,  and 
are  tranfparent,  and  the  thoracic  duel  conveys  the 
lymph  of  the  abdomen,  and  of  mofl  parts  of  the 
body,  to  the  blood  (liii.) 

CHAP.  XXVI. 

KIDNEYS,  BLADDER,  AND  URINE. 

DccLxxi.  ^ 8 ''HE  chyle,  when  taken  into  the  blood, 
I contains  a great  deal  of  water  ; the 
proportion  of  which  in  the  blood  would  be  too 
great,  and  its  feparation  into  the  cellular  fubftance 
too  eafy,  if  it  were  not  excreted.  A part  of  it  ex- 
hales  through  the  fkin,  (ccccxxxvi.)  and  another 
part,  as  large,  or  often  larger,  is  flrained  through 
the  Iddneys,  and  ejected  from  the  body. 

DCCLXxii.  The  kidneys  are  tv^o  vifeera,  placed 
behind  the  peritonseum,one  on  each  fide  of  the  fpine, 
incumbent  upon  the  diaphragm,  and  upon  the  pfoas 
and  quadratus  mufcles  of  the  loins,  but  fo  that  the 
right  kidney  is  commonly  placed  lower  and  more 
backwards.  Before  the  right  kidney  are  placed  the 
liver  upon  its  upper  part,  (dcxc.)  and  then  the  co- 
lon and  inteftines  ; before  the  lelt  kidney  arc  tl'.e 
fpleen,  ftomach,  pancreas,  and  alfo  the  colon.  1 hey 

are 


KIDNEYS. 


Chap.  XXVL 


are  tied  by  reduplications  of  the  peritonjeum  to  the 
colon,  duodenum,  liver,  and  fpleen.  Their  figure 
externally  is  convex,  and  femi-elliptical ; laterally 
they  are  flat,  and  inwardly  concave  ; they  are  un- 
equally divided  into  an  upper,  longer  and  thicker 
extremity,  and  into  a lower,  flat,  flender  extremity. 
They  are  firmly  invefted  by  a ftrong  external  denfe 
membrane,  which  does  not  come  from  the  perito- 
nscTam.  Betwixt  that  membrane  and  the  perito- 
naeum of  the  loins,  there  is  always  interpofed  a 
great  quantity  of  fat,  by  which  the  whole  furface 
of  the  kidney  is  furrounded  on  all  fides,  and  the 
nidus  is  completed,  which,  though  prepared  for  it, 
the  kidneys  would  not  totally  fill.  From  the  kid- 
ney the  peritonaeum  afcends  to  the  liver,  fpleen,  co- 
lon, and  diaphragm,  and  forms  as  it  were  ligaments 
for  the  kidney. 

DC  CL  XXIII.  The  veflels  of  the  kidneys  are  very 
large,  both  the  arteries,  which  together  exceed  the 
mefenterica,  and  the  veins.  The  arteries  arife  froiti 
the  aorta  under  that  of  the  mefentery,  not  always 
in  the  fame  manner,  yet  fo  that  the  left  is  common- 
ly fhortcr  than  the  right,  and  each  of  them  fre- 
quently in  two,  three,  or  four  trunks.  From  thefe 
arife  the  lower  capfular  arteries,  and  the  adipofe 
ones  belonging  to  the  fat  cortex  of  the  kidney 
(dcclxxii.)  and  not  unfrequently  the  fpermatics. 

; The  fat,  rather  than  the  kidneys,  receives  fmaller 
branches  from  the  fpermatic  and  lumbar  arteries. 

I The  arteries  are  thick,  fo  /that  the  proportion  of 
i their  coats  to  their  caliber  is  great ; that  they  are 
among  the  flrongeft  of  the  body ; 'and  that  they 
exceed  the  ftrength  of  the  aorta  by  one  third. 

DccLxxiv.  The  x^eins  are  large,  efpecially  the 
left,  and  lefs  inconftant  than  the  arteries  : the  right, 
which  is  often  without  a branch,  is  fliott  and  con- 
cealed ; the  left  always  receives  one  of  the  fperma- 
tics, and  the  capfular,  and  the  laft  branch  on  that 
fide  of  the  vena  fine  pari.  It  is  a very  large  vein, 

and 


KIDNEYS. 


Chap.  XXVI^ 


3S2 

and  accompanies  the  duodenum,  being  extended 
tranfverl'ely  a conliderable  way  to  the  left,  before 
the  aorta.  Both  the  arteries  and  veins  of  the  kid- 
neys arife  from  the  great  trunks  in  an  angle,  acute 
downwards,  and  both  divide  themfelves  into  feve- 
ral  branches  before  they  enter  the  kidney.  That 
the  pafi'age  of  the  blood  from  the  renal  arteries  into 
the  veins  is  very  quick,  appears  from  the  facility 
with  which  water,  wax,  or  air  pafs  that  way.  The 
uppermoft  veins  of  the  fat  of  the  kidneys  come  from 
the  capfular  veffels,  the  middle  from  the  renal  ones, 
and  the  lowermoft  from  the  fpermatics. 

DccLXxv.  There  are  lymphatic  veins,  of  confider- 
able  fize,  found  near  the  renal  veins,  where  they 
form  the  beginning  of  the  receptacle  of  the  chyle 
(dcclxiii.)  and  which  are  faid  to  receive  the 
branches  that  are  divided  under  the  external  coat 
of  the  kidney,  and  are  rendered  manifeft  by  putre- 
faftion,  or  by  the  injedfion  of  a fluid  into  the  renal 
arteries,  or  even  into  the  ureter. 

DCCLXxvi.  The  nerves  of  the  kidneys  are  fmall^ 
but  numerous  ; arifing  from  a confiderable  plexus, 
mixed  on  each  fide  with  ganglions,  which  is  gen- 
erated by  branches  of  the  great  femilunar  gan- 
glion, joined  with  others  coming  from  the  intercof- 
Eii  trunk,  from  within  the  thorax  itfelf.  They  en-* 
ter  the  kidney,  along  with  the  artery,  and  fend  off 
the  middle  mefenteric,  (dccxlviii.)  and  the  fperma- 
tic  nerves.  As  thefe  nerves  are  fmall,  they  give  but 
a fmall  degree  of  fenfibility  to  the  kidney. 

DccLxxvii.  Upon  the  top  of  each  kidney  Is  feat- 
ed  the  renal  capfule  ; which  in  the  foetus  is  large, 
even  larger  than  the  kidney  itfelf,  but  does  not  af- 
terwards increafe  in  the  adult : it  is  glandular,  of 
the  conglomerate  kind,  divided  into  lobes,  of  an 
oval  lhape  in  the  foetus,  and  triangular  in  the  adult ; 
that  on  the  ris^ht  fide  is  connecled  to  the  'iver  : the 
left  to  the  fpleen  and  pancreas  ; and  both  to  the  dia- 
pliragm  and  kidney,  by  as  many  fides.  From  care- 


Chap.  XXVI. 


KIDNEYS. 


383 

ful  obfervation,  it  feems  to  be  hollow  within,- fepa- 
rable  like  a ventricle,  with  the  internal  furfaces 
I'mooth,  as  if  cut,  full  of  a liquor  of  a yellowifh  red 
colour,  and  fluid,  almoft  like  blood.  The  arteries 
of  thefe  capfules  are  many,  and  of  three  kinds  ; the 
uppermoft  from  the  phrenics,  the  middle  ones  from 
the  aorta,  and  the  lower  ones  from  the  renals  ; the 
veins  are  one  on  each  flde,  the  right  one  going  to 
the  cava,  and  the  left  to  the  renal  vein.  The  faid 
vein  creeps  almoft  naked  through  the  very  fmooth 
ventricle,  in  the  fulcus  dividing  the  capfule,  and 
fends  branches  through  its  internal  furfaces.  Its 
ufes  are  as  yet  unknown  ; although  we  are  led  to 
believe,  that  it  is  fubfervient  to  the  kidney,  efpe- 
eially  in  the  foetus,  from  their  conftant  vicinity  in 
fo  many  animals.  It  has  no  excretory  du(ft,  nor 
does  it  difcharge  any  juice,  by  vifible  pores,  into 
the  vein. 

DccjLxxviii.  The  internal  fabric  of  the  kidney 
is  fimple,  and  known.  The  veflels  enter  the  inter- 
val between  the  upper  and  lower  portions  of  the 
kidney,  and  penetrate  into  its  fubftance,  furround- 
ed  with  a cellular  flieath,  and  divide  into  branches, 
which  run  between  the  branches  of  what  is  called 
the  pelvis,  along  the  columns  interpofed  betwixt 
the  papillae.  From  thence,  having  formed  arches 
both  in  the  papillae  and  between  them,  they  fur- 
round  the  origin  of  the  papillae,  nearer  to  the  peri- 
phery, fometimes  joined,  but  by  fmall  branches  : 
from  whence  proceed  innumerable  little  twigs,  of 
which  fome  return  by  the  intervals  between  the  pa- 
pillx  into  the  columns,  and  into  the  papillae  ; and 
others  tend  towards  the  external  furface  of  the  kid- 
ney, and  fometimes  pafs  through  the  coat  of  the 
kidney,  enter  into  its  adipofe  covering,  and  are 
there  changed  into  minute  ferpentine  twigs,  which 
being  reflected  towards  the  fame  portion  of  the  kid- 
ney from  whence  their  trunk  arofe,  they  are  grad- 
ually extended,  and  intermixed  with  the  urinifer- 

ous 


KIDNEYS. 


Chap.  XX\T 


ous  tubes.  But  from  the  cortex,  bundles  of  urlnif- 
erous  tubuli  arife  in  feveral  rays,  collected  in  great 
numbers  into  threads,  of  which  each  contains  many 
tubuli.  That  they  are  continuous  with  the  arteries, 
or  at  lead;  that  tliey  receive  their  branches  into 
them,  we  know,  from  experiments  which  Iliew  that 
water,  or  even  air,  palfes  eafily  from  the  arteries  of 
the  Iddneys  into  the  ureter  ; and,  laftly^  from  dif- 
cafes,  in  which  the  blood  itfelf  takes  the  fame  courfe. 
Between  thefc  papillae,  and  about  their  origin,  arc 
lituated  fome  roundifla  knots,  which  the  lateil  anat- 
omifts  conlider  as  arterial  glands,  producing  the 
proper  and  more  narrow  urinary  du(5ls.  Between 
thefe  dufts  many  arteries  run  parallel.  It  is  pro- 
bable, that  the  cortex  conhfts  of  curved  veffels, 
which  eminent  anatomifts  have  fuppofed  to  be  fmall- 
er  than  the  red  ones. 

DCCLXxix.  Thofe  uriniferous  vcfiels  gradually 
converge,  being  joined  together  like  rays,  and  in- 
fected in  great  numbers  into  one  blind  duel,  which 
duels  complete  the  reft  of  the  papilla,  and  terminate 
Cngly  in  its  convex  extremity  by  confpicuous  pores. 
The  number  of  thefe  papillse  is  not  altogether  cer- 
tain ; but  thirteen  or  more  of  them,  fimple,  triple, 
and  even  quadruple,  have  been  feen.  Thefe  were 
in  the  foetus  fo  dlfdncl,  that  the  kidney  then  appear- 
ed to  confift  of  as  many  diftin<T  fmaller  kidneys, 
connecled  together  by  loofe  cellular  membrane, 
each  of  which  was  furnifhed  with  its  proper  cortex- 
of  ferpentine  veffels,  and  its  compages  of  ftraiglit 
uriniferous  du6ls  ; the  bafis  of  all  of  tltcm  lay 
in  the  circumference  of  the  kidney,  and  their  ver- 
tices converged  towards  the  centre.  The  oppofitc 
cortices  of  two  of  thefe  little  kidneys  make  a col- 
umn, which  feparates  the  two  papillse.  In  the 
adult,  the  cellular  fubftance  being  condenfed,  draws 
the  papllke  clofer,  and  unites  them  into  one  kid- 
ney ; however,  it  again  almoll  recovers  the  condi- 
tion which  it  had  in  the  fcctus.  if  the  cellular  plates 


KiDNEYSa 


Chap.  XXVI. 


3^ 


are  relaxed  by  injecUng  water  into  the  veffels.  The 
kidney  is  alfo  larger  in  the  foetus  than  in  the  adult. 

DCCJLXXX,  Around  the  protuberant  furface  of  each 
papilla,  a loofe  membranous  diftind;  covering,  of 
larger  lize,  adheres  ; fo  that  the  papilla,  or  fome- 
times  two  contiguous  ones,  projed  into  the  hollow 
tube  of  this  cylindrical  funnel.  Two  or  three  of 
the  tubes  unite  together,  and  form  by  that  union 
three  hollow  trunks,  an  upper,  middle,  and  lower, 
which  again  unite,  but  on  the  outfide  of  the  kid- 
ney, into  one  conical  canal,  called  the  pelvis. 

DCCLxxxi.  The  blood  of  the  renal  artery  being 
lefs  moveable,  as  is  generally  believed,  than  that 
of  the  brain,  and  probably  containing  more  water, 
and  being  brought  by  the  ferpentine  arteries  of  the 
kidneys,  depolites  into  the  redilineal  tubes  of  the 
papillae  a great  portion  of  its  water,  and  the  oil  in- 
corporated  with  it,  and  the  falts,  and  any  thin  fluid 
it  may  contain.  But  the  fmaU  diameter  of  each 
Uriniferous  dud  at  its  origin,  and  its  firm  refiftance 
feem  to  exclude  the  grois  oil,  and  the  chyle,  and 
the  coagulable  lymph.  Hence,  the  increafed  celerity 
of  the  blood  fo  eaflly  forces  the  red  globules  through 
thefe  tubes,  and,  by  morbid  relaxation,  thej  tranf- 
mdt  the  true  fat  and  the  chyle,  and  the  falts  of  the 
meat  and  drink.  But  when  the  frrength  of  the  kid- 
ney is  reftored  by  aftringent  medicines,  the  urine 
returns  to  its  natural  ftate.  The  nerves  likewife 
have  a pov/er  of  contrading  or  relaxing  thefe  pafla- 
ges  ; and  thus  the  urine,  which  was  of  a yellow  col- 
our, fuddenly  becomes  watery  from  violent  affec- 
tions of  the  mind.  A vaft  quantity  is  prepared  ; 
equal  to  that  of  perfpiration,  o^r  fomewhat  greater. 

DCCLXxxii.  The  urine,  by  heat  or  putrefadion, 
fometimes  by  difeafe,  and  in  fome  animals  more  eafl- 
ly, changes  into  a volatile  alkaline  fllbftance,  inti- 
mately mixed  with  oil ; partly  empyreumatic,  yel- 
lov/,  and  volatile  ; and  partly  very  fixed,  feparable 
only  by  the  laft  degrees  of  fire,  called  phofphorus, 
B b a congealing 


KIDNEYS. 


Chap.  XXVI, 


386 

a congealing  fubftance,  fpontaneoufly  emitting  light, 
and  taking  fire  in  the  air  : and  with  earth  in  greater 
quantity  than  any  other  human  fluid,  both  creta- 
ceous and  fparry  ; the  latter  coming  chiefly  from 
the  drink,  the  former  alfo  from  the  folid  parts  of 
the  body  themfelves,  diiTolved  and  mixed  with  the 
blood.  But  there  is  alfo  fea-falt  in  frefh  urine,  and 
even  after  long  putrefaftion  it  is  found  in  the  phof- 
phorus,  although  a great  part  of  it  is  changed  into 
volatile  alkali.  Nor  is  the  urine  wholly  deftitute 
of  an  acid,  flmilar  to  the  vitriolic,  both  in  man  and 
in  animals.  There  is  alfo  a fait  obtained  from 
urine,  which  is  fufible  by  heat,  cooling  and  analo- 
gous to  nitre.  In  fevers,  the  oily  and  faline  parts 
of  the  urine  are  augmented  in  quantity  and  acri- 
monv. 

4 

DCCLXxxiii.  The  ureter,  continuous  with  the 
pelvis,  carries  on  the  urine  received  from  the  kid- 
ney, by  the  preflure  of  the  incumbent  vifcera,  and 
of  the  abdominal  and  lumbar  mufcles,  and  by  the 
blood  circulating  and  giving  impulfe  from  behind  ; 
and,  laftly,  by  the  weight  of  the  urine.  The  ure- 
ter, covered  by  the  peritongeum,  is  compofed  of  cel- 
lular membrane  ; then  of  a weak  and  obfcure  muf- 
cuiar  coat,  if  any  : then  a fecond  cellular  coat  ; a 
firm,  white,  nervous  one  ; a third  cellular  coat,  and 
an  innermoft  very  fniooth  memibrane,  porous  and 
glandular  internally ; and  it  is  in  general  moderately 
irritable.  It  is  of  diflerent  diameters  in  different 
places,  and  every  where  fwells  into  veficles.  It  de- 
fcoids  along  the  pfoas  mufcle,  acrofs  the  great  iliac 
vclfels,  arrives  into  the  pelvis  behind  the  urinary 
bladder  ; and,  at  the  union  of  the  defcending  and 
tranfverfe  portions  of  the  bladder,  enters  obliquely 
betwixt  the  mufcular  fibres  and  nervous  coat ; and 
dcfcends  betwixt  the  nervous  and  villous  coats,  for 
a conflderable  way  inwardly,  fo  that  the  mouths  of 
the  two  ureters  are  near  each  other,  and  open  by  a 
truncated  orifice.  They  have  no  valves,  cither  at 

their 


Chap.  XXVL 


KIDNEYS. 


3S7 

their  orifice,  or  in  any  part  of  their  courfe.  From 
their  infertion,  a protuberant  line  of  the  thickened 
nervous  coat  defcends  towards  the  caput  gaUinagx» 
nis. 

DccLkxxiVi  That  the  urine  is  feparated  in  the 
kidneys,  is  a matter  of  fact,  as  it  can  be  emulged 
from  its  canals  by  preffure.  That  it  defcends  by 
the  ureter,  is  fiiewn  by  the  furprifing  fw'eiling  of 
the  kidney,  and  of  that  part  of  the  ureter  which  is 
above  a ligature,  and  by  the  emptinefs  of  that  part 
which  is  below  it.  That  it  paiTes  into  the  bladder, 
is  alfo  proved,  by  the  immenfe  fwelling  of  the  ure- 
ters and  kidneys,  as  often  as  the  bladder  cannot  re-^ 
ceive  the  urine,  or  cannot  emit  it ; in  confequence 
of  an  obftacle  in  either  place. 

bccLxxxv.  Nor  does  the  urine  feem  to  come 
in  any  other  way.  For  although  it  be  certain,  that 
the  llomach,  like  all  other  membranes,  exhales ; al- 
though it  be  not  improbable,  from  experiments,  that 
the  bladder  alfo  abforbs  ; and  although  the  palTage 
of  acidulous  waters  be  extremely  quick  ; it  does  not 
follow,  that  there  is  a way,  different  from  the  ure- 
ters, to  convey  the  water  from  the  food  to  the  blad- 
der. For  the  bladder  is,  on  all  fides,  feparated  from 
the  cavity  of  the  abdomen  by  the  peritonaeum  ; nor 
is  it  afcertained  that  vapours,  either  exuding  from 
the  bladder,  or  tending  towards  it,  can  here  find 
open  pores  in  the  peritonaeum  ; and  membranes 
which  are  already  wetted  and  faturated  with  moif- 
ture,  do  not  imbibe  much.  But  the  urine  alfo  which 
is  contained  in  the  bladder,  diftends  it  even  fo  as 
to  occafion  death  ; and  does  not  find  any  paffage 
through  which  it  can  efcape  into  the  pelvis ; and  on 
the  other  hand,  when  the  ureters  are  obftrufted  with 
ftones,  fo  that  the  bladder  receives  nothing  from 
them,  it  is  either  quite  empty,  or  contains  a very 
acrid  and  thick  urine,  m.anifeftly  indicating  that  the 
water  can  find  no  way  from  the  pelvis  into  the 
bladder.  And  a careful  attention  to  the  manner  in 
B b 2 vdiich 


BLADDER. 


Chap. 


383 

which  mineral  waters  are  difcharged  by  urine,  de- 
monftrates,  that  there  is  no  fuch  rapidity  therein  as 
is  commonly  imagined  5 but  that  the  cold  of  the 
water  drunk,  like  external  cold  applied  to  the  Ikin, 
ftimulates  tlie  bladder,  fo  as  to  make  it  difchar^e 
immediately  the  urine  it  contains  already  fecreted, 
and  not  that  derived  from  the  drink  juft  taken. 
Again,  the  largenefs  of  the  renal  veflels  demon- 
ftrates,  that  not  much  lefs  than  an  eighth  part  of 
the  blood  of  the  whole  body  is  fent  to  the  kidneys  ; 
and,  confequentiy,  above  1000  ounces  of  blood  in 
an  hour  ; fo  that  it  is  not  farprifing  that  20,  or  even 
50  ounces  of  water,  are  feparated  from  the  blood  in 
that  fpace  of  time.  Finally,  it  is  certain,  that  both 
man  and  animals  perifh  if  the  ureters  be  tied  or  ob- 
ftruLfted ; nor,  in  thefe  circumftances,  is  any  urine 
found  in  the  bladder. 

nccLXXxvi.  The  urinary  bladder  is  feated  in  the 
cavity  of  the  pelvis,  which  is  an  appendix  to  the 
abdomen,  furrounded  almoft  on  aU  fides  by  bones  ; 
but  laterally,  and  at  the  bottom,  only  inclofed  by 
mufcles  ; and  in  every  dimenfion,  larger  in  women 
than  in  men.  it  is  fo  fituated  in  it,  as  to  cohere 
with  the  oflli  pubis  by  much  cellular  fubftance  ; 
then  it  receives  from  them  the  peritonseum,  which 
is  applied  to  a fmall  part  of  it  before ; but  Behind 
the  bladder,  it  defeends  for  a great  way,  almoft  as 
far  as  the  infertions  of  the  ureters  ; from  whence  it 
proceeds  ta  the  re<ftum,  or  to  the  uterus  in  women.. 
Behind  the  bladder,  the  feminal  veficies,  proftate 
gland,  reefum,  and  levatores  ani,  lie  under  it.  In 
the  foetus,  the  bladder  being  very  long,  and  coni- 
cal, extends  above  the  ofla  pubis  ; but  in  adults,  it 
hardly  ariies  above  thofe  bones,  even  when  inflat- 
ed, becaufe,  in  them,  the  pelvis  is  much  larger  and 
deeper  in  proportion  to  the  body. 

DccLxxxvii.  The  figure  of  the  bladder  is,  in  gen- 
eral, oval,  but  its  anterior  furface  is  flatter,  its  pof- 
terior  more  convex,  and  its  inferior  obtufe  vertex, 

which 


Chap.  XXVI. 


BLADDER. 


3S9 

which  refts  upon  the  rectum,  is  very  flat  and  broad. 
Such  is  the  figure  of  it  in  the  male  adult : in  the 
foetus  it  is  almofl:  cylindrical ; and,  in  women,  who 
have  had  many  children,  it  is  fo  much  flattened  lat- 
erally, that  it  refembles  a roundifli  tetrahedral  fig- 
ure, of  which  the  fections  are  triangular.  This 
change  feems  to  arife  from  the  weight  of  the  urine, 
which  deprefles  the  lower  parts  of  the  bladder,  and 
extends  it  in  breadth,  fo  as  to  render  it  fliorter  and 
broader.  It  is  of  different  magnitudes  ; fo  that,  in 
fome  difeafes,  from  irritation,  and  habitual  contrac- 
tion, it  becomes  very  fmall, 

DCCLXxxviii.  The  fabric  of  the  bladder  is  much 
like  that  of  all  large  membranous  receptacles.  The 
firft  membrane  is  cellular  ; in  its  forepart  lax,  and 
replenifhed  with  fat ; behind,  it  is  lefs  fo,  where  it 
alfo  unites  with  the  redum.  In  this,  there  is  a net- 
work of  veffels,  chiefly  of  veins.  Next  to  this  fol- 
lows the  mufcular  coat,  which  is  very  difixcult  to 
deferibe,  conflfting  of  pale  contracHle  fibres,  difpof- 
ed  in  various  reticulated  bundles,  not  continuous, 
but  with  intervening  fpaces,  in  which  the  nervous 
coat  lies  uncovered.  The  principal  ftratum  of  thefe 
is  longitudinal ; which,  arifmg  before  from  the  prof- 
tate  gland,  and  frequently,  though  not  always,  fo 
connected  to  the  fynchondrofis  of  the  offa  pubis,  or 
the  membranes  covering  it,  as  feemingly  to  arife 
from  thence,  afeend  towards  the  conical  fuperior 
extremity  of  the  bladder  ; defeend  over  it,  along  the 
pofterior  furface,  become  at  that  place  very  broad, 
and  again  terminate  at  the  proftate  ; but  at  the  fides 
they  diverge,  varioufly  palmated,  and  are  blended 
from  the  anterior  and  pofterior  planes.  Thefe  fi- 
bres muft  deprefs  the  bladder,  and  confequentiy 
propel  the  urine  towards  its  lower  part. 

DccLxxxix.  The  remaining  fibres  are  very  difii- 
eultiy  reduced  to  any  order.  They  fill  the  inter- 
vals of  the  former  ; arifing  from  the  proftate,  then 
infleded,  they  afeend,  and  form  a ftratum,  partly 

oblique, 


390 


BLADDER. 


Chap.  XXVL 


oblique,  and  partly  tranfverfe,  the  interior  ones 
more  fo  than  the  others,  both  in  the  forepart  and 
back  part  of  the  bladder. 

Dccxc.  The  contracfile  force  of  th?  bladder  is 
gentle,  but  perpetual ; fo  that  it  contracts  from  its 
greateft  dilatation  to  its  fmaileft  diameter,  without 
any  alternate  relaxation,  and  remains  long  in  its 
Rate  of  greateft  contraction.  The  urine  is  its  leaft 
uneafy  fdmulus  ; water  injected  is  more  fo  ; and 
calculus,  and  every  kind  of  irritation,  the  molt  in- 
fufferable.  When  immoderately  diftended,  it  lofes 
its  powers ; fo  that  either  it  cannot  expel,  or  it  can- 
not retain  the  urine. 

Dccxci.  Within  the  mufcular  coat  is  fpread  the 
fecond  cellular  ftratum,  of  an  elegant  fabric,  inflat- 
able, more  tender,  and  fofter  than  in  the  intcftines. 
Next  follows  the  nervous  coat,  continuous  with  the 
fkin,  and  acutely  fenfible  ; the  innermoft,  refem- 
bling  that  of  the  fhomach,  is  lafl: ; more  obfcui'e  ; 
diflicultly  feparable  from  the  nervous  one  ; conti- 
nuous with  the  epidermis  ; and,  like  it,  eafily  re- 
parable, extremely  mucous,  and  folded  into  various 
wrinldes,  without  any  certain  order.  In  it,  the 
pores  of  the  cryptse  fometirnes  appear,  but  not  al- 
ways eaflly,  pouring  out  a vifcid  and  bland  gluten. 
The  mucus  itfeif  is  very  manifeft,  and  is  prepared 
in  greater  quantity  in  proportion  to  the  irritation 
of  the  bladder.  It  is  of  the  greateft  importance  for 
diminilhing  the  irritation  of  the  acrid  urine. 

Dccxcii.  The  veflels  and  nerves  of  the  bladder 
coincide  with  thcfe  which  go  to  the  genital  parts, 
where  we  Ihall  defer ibe  them.  Thofe  which  come 
from  the  epigaftrics  are  fmall.  Their  principal  re- 
ticulation is  in  the  ftrft  cellular  ftratum,  and  there 
is  another  in  the  fecond.  Through  the  villous  coat 
the  exhaling  arteries  exhale,  as  we  learn  by  experi- 
ment, from  anatomical  injeclions  ; and  the  abforb- 
ing  veins  open,  to  which  are  owing  the  greater 
conftftence  and  higher  colour  of  the  urine,  wJicn 

retained. 


Chap.  XXVI. 


BLADDER. 


391 

retained.  The  lymphatic  veffels  in  the  outer  cellular 
ftratum,  are  eahly  demonftrated  ; but  their  origin 
is  probably  foreign  from  the  adjacent  inteftine. 

Dccxcm.  The  urinary  bladder  is  of  the  fame 
nature  with  other  membranous  facs,  fo  that  it  both 
tranfmits  water  from  its  cavity  through  the  inor- 
ganic pores  of  its  membranes,  and  abforbs  water 
when  immerfed  in  it. 

Dccxciv.  Into  this  bladder,  the  urine  flows,  in 
one  uniform  ftream,  as  has  been  proved,  in  morbid 
and  uncommon  cafes,  in  which  the  extremities  of 
the  ureters  were  vilible  to  the  eye,  and  there  re- 
mains, and  becomes  more  acrid  and  higher  colour- 
ed, from  the  abforption  of  its  water.  We  are  not 
fully  acquainted  with  the  caufe,  which  retains  the 
urine  in  the  bladder.  The  fphinfler  is  obfcure  ; the 
deprellion  of  the  bladder  feems  to  affifl,  which  be- 
ing convex,  defcends  upon  the  recfum,  behind  the 
fphincfler,  below  its  orifice,  fo  that  the  urine  does 
not  reach  the  orifice  of  the  urethra  till  collected  in 
fome  quantity.  It  is  certain,  that  the  urine  does 
not  efcape  fpontaneoufly  even  from  the  dead  body. 

Dccxcv.  At  length,  the  urine,  by  its  bulk  and 
acrimony,  irritating  the  fenfible  fabric  of  the  blad- 
der, is  expelled,  firft  by  the  motion  of  the  dia- 
phragm and  abdominal  mufcles,  by  the  preflure  of 
which,  impelling  the  inteftines  againfl;  the  bladde? 
in  the  ere6f  pofture,  the  urine  makes  itfelf  a way 
through  the  narrow  and  impeded  paflage  ; and  fec- 
ondly,  by  the  periftaltic  motion  of  the  bladder  it- 
felf, arifing  from  the  contraction  of  its  mufcular 
fabric  (dcclxxxviii.  et  feq.) 

Dccxcvi.  By  the  urine,  befides  the  water,  and 
part  of  our  food,  much  matter,  that  is  noxious  to 
the  human  body,  feems  to  pafs  off ; efpecially  cal- 
careous earth  reforbed  from  the  bones  and  folid 
parts,  and  which  would  produce  bony  crufts  and 
calculi  wherever  it  was  retained ; the  fparry  earth 
of  waters  j an  acrid  oil  mixed  with  fait,  fo  as  to  af- 

fume 


392 


BLADDER. 


Chap.  XXVI. 


fume  a volatile  nature.  The  urine,  by  its  retention, 
difpofes  to  the  generation  of  calculi,  and  to  gout : 
when  fuppreffed,  it  produces  acute  fev^ers  ; and  laft- 
ly,  flows  back  to  the  brain,  and  is  depofited  on  it, 
and  deftroys  it. 

Dccxcvii.  From  the  obtufe  vertex  of  the  bladder, 
not  exactly  from  its  bottom.,  but  further  forwards, 
a canal  with  a fmall  orifice,  continuous  with  the 
bladder,  arifes.  It  is  denominated  the  urethra,  and 
is  compofed  of  an  internal  membrane,  which  is  evi- 
dently continuous  with  the  epidermis,  of  furround-r 
ing  cellular  fubftance,  and  of  a firm  nervous  coat. 
It  is  variable  in  its  diameter  and  direction  ; in  wo^ 
men,  it  is  ftraight,  tranfverfe,  and  flrort.  I do  not 
find  a valve  in  its  orifice, 

Dccxcviii.  The  urethra  is  at  firfi:  furroundcd  on 
all  fides,  by  the  profiate  gland ; it  then  proceeds 
naked,  for  a fmall  fpace  ; it  is  then  embraced  by  the 
bulb  immediately  attached  to  it,  firft  below,  and 
then  above  ; it  is  then  received  in  the  interval  be- 
tween the  corpora  cavernofa  of  the  penis,  contigu- 
ous to  it  above,  and  laterally,  and  acquires  ftrength 
and  the  ftate  of  an  open  tube  from  them.  I'he 
urethra  is  widefi;  where  it  arifes  from  the  bladder  ; 
it  contracts  itfelf  conically  in  the  profiate  ; in  its 
naked  part  it  is  cylindrical ; it  enlarges  at  the  firft 
accefiion  of  the  bulb  ; in  the  penis  it  is  alfo  cylin- 
drical, and  again  dilates  itfelf  a little  before  its  ter- 
mination. 

Dccxcix.  This  canal  is  governed  by  various  muf- 
cies,  either  proper  or  contiguous,  And  firft,  in 
women,  there  are  manifeftly  fibres  placed  round 
the  egrefs  of  the  incipient  urethra,  which  are,  on 
tlie  v/hole,  tranfverfe,  but  varioufly  decufl'ating  each 
other  ; of  which  the  fixed  point  is  in  the  vagina, 
and  the  office  is  evidently  that  of  a fphincTer,  to 
deprefs  the  canal,  about  the  opening  of  which  they 
are  clifpofed,  and  to  clofe  it  againft  the  refilling 
contracted  vagina,  and  fphinfler  of  the  anus.  In 

man, 


Chap.  XXVI. 


BLADDER. 


393 

man,  fimilar  tranfverfe  fibres,  but  forming  an  arch 
upwards,  run  into  the  conjunction  of  the  bladder, 
with  the  proftate  ; both  covering  a longitudinal 
bundle  of  fibres  and  the  proftate,  and  covered  by 
thefe  fibres,  they  are  to  a certain  degree  fitted  for 
contracting  the  orifice  of  the  bladder. 

Dccc.  The  firft  tranfverfe  mufcle  proceeding tranf- 
veriely  from  that  branch  of  the  ifchium  which  fends 
forth  the  ereCtor  mufcle  of  the  penis,  towards  the 
other  os  ifchium,  partly  paffes  into  it,  partly  is  inferr- 
ed into  the  middle  of  die  bulb  of  the  urethra,  and 
partly  degenerates  into  the  accelerator.  It  preffes 
upon,  fhakes,  and  draws  backwards  the  bulb  of  the 
urethra.  The  other,  produced  from  the  branch  of 
the  os  ifchium,  is  inferred  into  the  ifihmus  of  the 
urethra  before  the  bulb,  and  dilates  it. 

DCCC  I.  But  like  wife  the  levator  of  the  anus  feems 
to  ralfe  the  urethra  againfi;  the  os  pubis,  and  to 
fhut  the  exit  from  the  bladder  ; and  the  conftric- 
tion  of  the  accelerator,  together  with  the  fphinfter, 
’is  eafily  perceived  in  the  living  body,  as  it  per- 
fectly clofes  the  mouth  of  the  bladder,  and  checks 
the  urine  even  while  it  is  flowing  ; whence  there 
is  no  doubt,  that  the  moderate  tenfion  of  this  muf- 
cle contributes  towards  retaining  the  urine. 

Dcccii.  An  effort  being  now  made,  (dccxcv.)  by 
the  prefi’ure  of  the  diaphragm,  the  urine  is  ejedted 
with  greater  celerity,  as  it  com.es  from  a large  re- 
ceptacle, through  a narrow  canal ; and,  being  dif- 
charged,  the  body  is  freed  from  the  uneafy  fenfa- 
tion.  The  laft  drops,  which  remain  in  the  loweft  part 
of  the  bulb,  and  are  retained  there  by  their  weight, 
are  expelled  by  the  accelerator  mufcle,  which  is  4 
ftrong  mufcular  expanlion,  placed  round  the  bulb 
of  the  urethra,  with  pennated  fibres,  meeting  in  the 
bottom  middle  part  of  the  bulb,  faftened  before  by 
two  tendons  to  the  cavernous  bodies  of  the  penis 
behind,  and  connected  by  three  mufcular  portions 
to  the  fphincter  of  the  anus,  of  which  two  are  lateral, 

and 


BLADDER. 


Chap.  TlYt 


394 

and  one  central,  with  fome  acceillon  from  the  tranf- 
verfe  mufcles.  This  mufcle,  when  the  fphincter  is 
fteady  and  ihut,  draws  the  bulb  upwards  ; and, 
acting  upon  the  urethra  alternately,  with  confider- 
able  force,  expels  the  laft  drops  of  the  urine. 

Dccciii.  We  cannot  admit,  that  the  pyramidal 
mufcle  of  the  abdomen,  draws  the  bladder  down- 
wards from  the  bundle  of  umbilical  veffels,  and  re- 
laxes it,  and  fits  it  for  the  action  of  the  long  muf- 
cular  fibres,  as  the  mufcle  itfelf  is  often  wanting  ; 
as  it  cannot  deprefs  the  bladder,  and  very  rarely 
reaches  the  navel. 

Dccciv.  But  as  the  urine  is  acrid,  and  the  mem- 
brane of  the  urethra  very  fenfible,  and  as  the  air 
can  be  admitted  into  it,  nature  has  fupplied  this 
canal  with  a large  quantity  of  mucus.  Befides  its 
fources  in  the  bladder,  this  mucus  is  generated,  in 
the  firfi:  place,  by  two  conglomerate  glands  ; one 
of  which  is  feated  on  each  fide,  in  the  angle  be- 
twixt the  bulb  of  the  urethra  and  the  cavernous 
body  of  the  penis,  and  fends  out  a duel,  running 
for  a confiderable  way  obliquely  along  the  urethra, 
and  inferted  before  its  bulb.  I am  ignorant  of  any 
gland  of  the  ifthmus  different  from  the  cellular  tex- 
ture. Moreover,  the  whole  urethra  is  full  of  cy- 
lindrieal  mucous  finufes,  moft  of  which  defeend 
towards  the  glans,  though  fome  run  in  a contrary 
dii'eclion,  into  whofe  fides  minute  cryptee  depofite 
a fluid  and  bland  mucus.  The  iargeft  of  thefe 
fmufes  are  difpofed  in  a feries  along  the  upper  fide 
of  the  urethra,  beginning  before  the  bulb,  and  ex- 
tending to  the  origin  of  the  glans.  The  fmall 
ones  are  both  mixed  with  thefe  large  ones,  and  dif- 
pofed on  the  lides.  In  women,  they  are  numerous 
and  large  in  their , fliort  urethra,  efpeciaUy  at  its 
opening. 

Dcccv.  The  neceffary  propriety  of  human  life 
requires  the  detention  of  the  urine.  But  this  very 
utility  is  attended  with  the  danger  of  difeafe,  finte 

the 


Chap.  XXVII.  MALE  GENITALS.. 


395 

the  urine  when  at  reft,  immediately  depohtes  its 
earthy  particles,  which  by  the  acceffion  of  new  ftrata, 
form  calculi.  But  the  great  number  of  people  free 
from  calculi,  ihow,  that  the  very  lubricous  mucus 
of  the  bladder  is  a fullicient  protection,  unlefs  the 
ufe  of  fabulous  and  tophaceous  water,  of  wine,  or  of 
vifcid  aliments,  exceflive  inactivity,  preternatural  re- 
tention of  the  urine,  the  prefence  of  fome  vifcid 
body  to  attract  the  calculous  earth,  and,  finally,  ne- 
phritic difeafes,  afford  a fuperabundance  of  calcu.? 
lous  earth,  or  a nucleus  for  its  adhefion. 


CHAP.  XXVII. 

MALE  ORGANS  OF  GENERATION. 

Dcccvi.  ''  I 'HE  veffels  belonging  to  the  genitals 
§ arife  near  the  kidneys,  almoif  in  ev- 
ery kind  of  animals.  This  is  occafioned  by  the  op- 
portunity of  deriving  a double  ufe  from  one  organ, 
w'hich  might  difcharge  both  the  urine  and  the  fe- 
men,  and  by  the  relation  of  the  genital  parts  to  the 
interval  between  the  tops  of  the  thighs,  which  is 
fubfervient  to  cleanlinefs,  modefly,  the  facility  of 
parturition,  of  making  water,  and  to  the  effed.  of 
the  efforts  employed  in  thefe. 

Dcccvii.  The  male  femen  is  formed  in  the  tef- 
ticle  ; is  depofited  in  the  feminal  veficles ; is  eject- 
ed from  the  penis  ; is  injected  into  the  uterus,  and 
fecundates  the  ovum.  Such  is  the  arrangement  we 
fliall  follow.  The  human  tefticles,  fmaU  in  pro- 
portion to  the  body,  in  the  foetus,  when  very  young, 
are  lodged  within  the  peritonaeum,  and  gradually 
defcend  under  it  into  the  groins,  and  when  it  has 
arrived  at  maturity,  they  lie  below  the  groins ; 
their  fituation  being  changed,  perhaps  by  the  fimple 
force  of  their  weight,  and  of  the  influx  of  blood  ; 
yet  fometimes  they  remain  in  the  groin,  even  in 

adults. 


MALE  GENITALS.  Chap.  XXW. 


adults.  They  defcend  by  a cellular  paflage,  which 
in  the  fetus  is  open,  and  called  the  proccfs  leading 
from  the  cavity  of  th^  peritonaeum  into  the  fcro- 
tum  ; and  the  fame  paffage,  after  the  tehicle  is 
tranfmittcd,  is  contracted  and  obliterated  by  a law 
of  nature. 

Dcccviii.  The  tefcicles  are  defended  by  various 
integuments.  In  the  firft  place,  they  are  iurrour.d- 
ed  by  the  fcrotum,  which  is  formed  of  a denfe  cel- 
lular coat,  vafcular  and  compacled  into  a folid  mem- 
brane, clofely  adhering  to  the  Ikin,  which  pofTefTes 
fome  elaftic  motion  from  cold  and  during  venery, 
but  without  any  mufcular  fabric,  although  when  it 
acts  it  becomes  corrugated,  and  draw^  up  the  tef- 
ticles.  This  cellular  coat,  commonly  called  the 
dartos,  is  placed  round  each  of  the  tefticles  feparate- 
ly ; therefore,  at  their  union,  they  form  a kind  of 
feptum,  in  a dry  preparation  ; this  feptum  is  often 
imperfect  in  its  upper  part,  near  the  penis. 

Dcccix.  The  dartos  is  interiorly  relaxed  into  cel- 
lular fubftance,  which  is  inflatable  as  in  other  pla-. 
ces,  but  without  fat,  except  in  the  lower  part  of 
the  fcrotum.  Next  follovrs  a mufcle,  from  its  oL 
lice  called  crem after  ; which  arifes  from  the  degen- 
erating fibres  of  the  lefs  oblique  mufcle  of  the  ab- 
domen, and  from  the  tendon  of  the  obliquus  ex- 
ternus,  which  has  got  the  name  of  a ligament,  and 
fometimes  from  other  fibres  defcending  from  the 
os  pubis,  and  being  expanded  into  a vagina,  and 
furrounding  the  tefticle  behind,  and  then  on  all 
fidcs,  it  comprefles,  elevates,  and  emulges  it. 

Dcccx.  Next  to  this  follows  the  fecond  cellular  • 
ftratum,  v/hicli  is  continuous  with  the  exterior 
fpongy  web,  which  furrounds  the  pcritonxum  ; 
this  is  called  the  tunica  vaginalis.  It  is  compofed 
of  lonsrer  cells  than  clfewliere,  wliich  may  be  inflat- 
ed one  after  another.  At  the  beginning  of  the 
tefticie,  above  the  epididymis,  part  of  the  va- 
ginal coat,  which  furrounds  the  tefticle,  is  lb  fepa- 


Chap.  SXVIL  MALE  GENITALS.  jpf 

rated  from  the  rell,  which  lies  higher  than  the  tefti»= 
cle  towards  the  ring  of  the  abdominal  muicles,  as 
almoft  to  prevent  the  tranfmiffion  of  air.  Betwixt 
this  membrane  and  the  following,  there  is  a fpace, 
into  which  vapour  is  exhaled,  and  fometimes  a little 
water  is  cohered.  The  innermoft  coat  of  the  tef- 
ticle,  called  the  albuginea,  is  a Itrong,  white,  com- 
pa£t  membrane,  wliich  immediately  invefls  the  fub- 
ftance  of  the  tellicle. 

Dcccxi.  The  tefticle  properly  fo  called,  is  of  an 
oval  figure,  with  an  acute  vertex,  directed  up^ 
wards  and  a little  outwards.  The  epididymis  is  a 
kind  of  addition  to  the  tefticle  ; a flat  thick  tape, 
which  goes  round  the  pofterior  margin  of  the  teft 
tide,  to  which  it  is  conneded  by  cellular  texture, 
and  by  veflels.  Below  it  is  flatter  ; on  the  upper 
part  it  adheres  to  the  tefticle  by  a thick  and  con- 
vex head,  as  it  alio  does  at  the  very  bottom.  In 
the  middle,  it  is  partly  attached,  and  being  partly 
loofe,  forms  a Ihut  cavity. 

DcccxiL  To  the  tefticle  the  fpermatic  arteries 
defcend,  one  on  each  fide,  arifing  from  the  aorta 
below  the  renal  arteries  ; but  not  unfrequently 
from  the  renals  themfelves,  or  from  one  of  the  cap- 
fulary, or  from  the  aorta  itfelf  above  the  renal. 
This  artery,  the  fmalleft  in  the  body  in  proportion 
to  its  length,  defcends  outwards  before  the  pfoas 
mufde,  and  gives  frnali  branches  to  the  liver,  the 
fat  of  the  kidney,  the  ureter,  lumbar  glands,  mefo- 
colon,  peritonseurn,  and  efpecially  a remarkable 
adipofe  branch,  bent  around  the  bottom  of  the  kid- 
ney : and,  without  becoming  lefs,  it  proceeds  be- 
hind the  peritonaeum,  as  far  as  the  ring  of  the 
abdomen.  This  ring  is  formed  entirely  of  the  ten- 
dinous fibres,  defcending  from  the  external  oblique 
mufcle,  interrupted  by  a long  aperture,  grov/ing 
wider  downwards  ; a great  many  of  which,  ftender 
and  interior,  are  partly  inferted  extenfively  into 
the  middle  of  the  os  pubis,  and  partly  decuflate 


MALE  GENITALS.  Chap.  XXVIL 


55S 

and  unite  with  the  fibres  of  the  mufcle  of  the  op^ 
polite  fide  ; thefe  are  called  the  inner  coluinni 
Other  external  ftronger  fibres,  feparated  from  the 
former  by  the  aperture,  are  inferred  in  a thick  bun- 
dle into  the  outer  fide  of  the  os  pubis,  under  the 
denomination  of  the  external  column  : from  it  va- 
rious fibres  run  off  to  the  fafcia  lata  and  groin. 
The  upper  part  of  this  opening  is  in  fome  meafure 
clofed  up  by  fibres,  arifing  from  the  outer  column j 
ihllefted  and  afcending  along  the  inner  and  weaker 
column.  Below  thefe  fibres,  through  the  fmall 
opening  left,  which  is  often  divided  b}"  tendinous 
fibres,  the  fpermatic  artery  defcends,  along  with 
the  vein,  and  vas  deferens,  formed  into  a cylindrical 
cord,  with  a good  deal  of  cellular  fubftance,  before 
the  external  column,  but  does  not  perforate  the 
peritonaeum,  which  lies  before  it  through  its  whole 
extent.  At  this  ring,  the  duclus  deferens  is  joined 
wnth  the  rope  of  vefl'els,  and  the  whole  bundle  pro- 
ceeds into  the  groin,  and  afterwards  into  the  fcro- 
tum.  The  fpermatic  artery  gives  many  branches 
to  the  cremafter,  to  the  cellular  coat,  and  to  the 
feptum  of  the  fcrotum  ; and  defcends  in  two  plex- 
ufes  to  the  tefticle  ; of  which  the  principal  palfes 
betwixt  the  epididymis  and  origin  of  the  vas  de- 
ferens, to  the  middle  and  lower  part  of  the  tefticle, 
and  is  diftributed  in  tranfverfe  branches,  through 
the  albuginea  : the  other  plexus  goes  to  the  tefticle 
in  company  with  the  vas  deferens,  has  a like  termi- 
nation, and  is  varioufly  inofculated  with  the  former. 
Other  fmall  arteries  go  to  the  coverings  of  the  tef- 
ticle from  the  epigaftrics,  and  others  from  thofe  of 
the  bladder,  accompanying  the  vas  deferens ; both 
of  which  communicate  with  the  fpermatic  veffels. 

Dcccxiii.  Thefe  very  numerous  arteries  play  a- 
bout  the  epididymis  ; but  the  larger  of  them  fpread 
tranfverfely  through  the  albuginea,  which  they  per- 
forate in  fevcral  places,  and  enter  into  the  inner- 
moft  fubftance  of  the  tefticle,  through  v hich  they 

are 


Chap.  XSVII.  MALE  GENITALS.  399 

are  every  where  diftributed  upon  the  numerous 
membranous  feptuia.  There  is  no  larger  anafto- 
moiis  or  communication  betwixt  the  fpermatic  ar^. 
tery  and  vein  here,  than  in  other  parts,  nor  are  the 
branches  .within  the  albuginea,  received  into  the 
tefticle,  without  blood.  But  the  long  courfe  of  this 
artery,  the  fmallnefs  of  its  diameter,  the  ferpentine 
flexures,  the  great  proportion  of  the  branches  to 
the  trunk,  and  their  cold  fituation,  demonftrate, 
that  the  blood  arrives  at  the  tefticle  flowly,  and  in 
final!  quantity. 

Dcccxiv.  The  right  fpermatic  vein  carries  its 
blood  to  the  cava  ; the  left  to  the  emulgent  vein, 
or  to  both  : it  is  enormoufly  larger  than  the  artery, 
both  in  its  trunk  and  branches  and  accompanies 
it,  but  more  plentifully,  having  feveral  trunks  in- 
terwoven into  a very  long  reticulated  "web  within 
the  abdomen,  which  furrounds  the  artery,  and  is 
continued  into  the  tefticle,  by  degrees  dividing  in- 
to two  like  the  artery.  There  are  fome  valves  in 
this  vein,  though  few. 

ncccxv.  The  external  coverings  of  the  tefticle 
have  their  arteries  from  the  epigaftrics  ; the  fcro- 
tum  from  the  crural  arteries,  and  from  the  internal 
branch  of  them,  v/hich  is  called  the  external  pu- 
denda ; the  core efpondent  veins  go  to  the  faplnena, 
and  to  the  crural  veins. 

Dcccxvi.  The  nerves  of  the  tefticle  are  many, 
whence  its  fenftbility  is  peculiarly  acute,  fo  that 
injuries  of  the  tefticle  are  immediately  followed  by 
faintings  and  convulfions,  and  particularly  by  lock- 
ed jaw.  Some  of  them  arife  deep  from  the  renal 
plexus,  from  the  great  mefenteric  plexus,  from  the 
trunk  of  the  intercoftal  nerve,  and  laftly  from  the 
mefocolic  plexus,  and  follow  the  courfe  of  the 
fpermatic  veffels.  Others,  more  fuperficial,  defeend 
to  the  coverings  of  the  tefticle,  from  the  fecond, 
tliird,  and  fourth  pair  of  the  lumbar  nerves. 

DCCCXVII. 


MALE  GENITALS.  Chap.  XX^TL 


3.9  S 

and  unite  with  the  fibres  of  the  mufcle  of  the  op- 
pofite  fide  ; thefe  are  called  the  inner  column. 
Other  external  ftronger  fibres,  feparated  from  the 
former  Iry  the  aperture,  are  inferted  in  a thick  bun^ 
die  into  the  outer  fide  of  the  os  pubis,  under  the 
denomination  of  the  external  column  ; from  it  va- 
rious fibres  run  off  to  the  fafcia  lata  and  groin. 
The  upper  part  of  this  opening  is  in  fome  meafure 
clofedup  by  fibres,  arifing  from  the  outer  column, 
inflected  and  afcendihg  along  the  inner  and  weaker 
column.  Below  thefe  fibres,  through  the  fmall 
opening  left,  which  is  often  divided  by  tendinous 
fibres,  the  fpermatic  artery  defcends,  along  with 
the  vein,  andvas  deferens,  formed  into  a cylindrical 
cord,  v/ith  a good  deal  of  cellular  fubftance,  before 
the  external  column,  but  does  not  perforate  the 
peritdnseum,  which  lies  before  it  through  its  whole 
extent.  At  this  ring,  the  ductus  deferens  is  joined 
with  the  rope  of  veflcls,  and  the  Vv*hole  bundle  pro- 
ceeds into  the  groin,  and  afterwards  into  the  fcro- 
tum.  The  fpermatic  artery  gives  many  branches 
to  the  cremafler,  to  the  cellular  coat,  and  to  the 
feptum  of  the  fcrotum  ; and  defcends  in  two  plex- 
ufes  to  the  tefiicle  ; of  which  the  principal  pafles 
betwixt  the  epididymis  and  origin  of  the  vas  de- 
ferens, to  the  iTiiddle  and  lower  part  of  the  tefticle, 
and  is  diftributed  in  tranfverfe  branches,  through 
the  albuginea  : the  other  plexus  goes  to  the  tefticle 
in  company  with  the  vas  deferens,  has  a like  termi- 
nation, and  is  varioufly  inofculated  with  the  former. 
Other  ftnall  arteries  go  to  the  coverings  of  the  tef- 
ticle from  the  epigaflrics,  and  others  from  thofe  of 
the  bladder,  accompanying  the  vas  deferens  ; both 
of  which  communicate  with  the  fpermatic  velTels. 

Dcccxiii.  Thefe  very  numerous  arteries  play  a- 
bout  the  epididymis ; but  the  larger  of  them  fpread 
tranfverfely  througlt  the  albuginea,  which  they  per- 
forate in  fevered  places,  and  enter  into  the  inncr- 
mofl  fubftance  of  the  tefticle,  through  which  they 


Chap.  XXVII.  MALE  GEmXALS. 


399 

are  every  where  diflributed  upon  the  numerous 
membranous  feptula.  There  is  no  larger  anafto- 
mofis  or  communication  betvdxt  the  fpermatic  ar- 
tery and  vein  here,  than  in  other  parts,  nor  are  the 
branches  within  the  albuginea,  received  into  the 
tefticle,  without  blood.  But  the  long  courfe  of  this 
artery,  the  fmallnefs  of  its  diameter,  the  ferpentine 
flexures,  the  great  proportion  of  the  branches  to 
the  trunk,  and  their  cold  lituation,  demonftratCj 
that  the  blood  arrives  at  the  tefticle  flowly,  and  in 
fmali  quantity. 

Dcccxiv.  The  right  fpermatic  vein  carries  its 
blood  to  the  cava  ; the  left  to  the  emulgent  vein, 
or  to  both  : it  is  enormoufly  larger  than  the  artery, 
both  in  its  trunk  and  branches  ; and  accompanies 
it,  but  more  plentifully,  having  feveral  trunks  in- 
terwoven into  a very  long  reticulated  w^eb  within 
the  abdomen,  v/hich  furrounds  the  artery,  and  is 
continued  into  the  tefticle,  by  degrees  dividing  in- 
to two  like  the  artery.  There  are  fome  valves  in 
this  vein,  though  few. 

Dcccxv.  The  external  coverings  of  the  tefticle 
have  their  arteries  from  the  epigaftrics  ; the  fcro- 
tum  from  the  crural  arteries,  and  from  the  internal 
branch  of  them,  which  is  called  the  external  pm 
denda ; the  correfpondent  veins  go  to  the  faphaena, 
and  to  the  crural  veins. 

Dcccxvi.  The  nerves  of  the  tefticle  are  many, 
whence  its  fenftbility  is  peculiarly  acute,  fo  that 
injuries  of  the  tefticle  are  immediately  followed  by 
faintings  and  convulftons,  and  particularly  by  lock- 
ed jaw.  Some  of  them  arife  deep  from  the  renal 
plexus,  from  the  great  mcfenteric  plexus,  from  the 
trunk  of  the  intercoftal  nerve,  and  laftly  from  the 
mefocolic  plexus,  and  follow  the  courfe  of  the 
fpermatic  veffels.  Others,  more  fuperficial,  defcend 
to  the  coverings  of  the  tefticle,  from  the  fecond, 
third,  and  fourth  pair  of  the  lumbar  nerves. 

Daccxvii. 


MALE  GENITALS.  Chap.  XXm 


460 

Dcccxvii.  I hare  frequently  obferved  lymphatic 
veffels  in  the  fpermatic  cord,  which  are  belie^^ed 
to  arife  from  the  tefticle  itfelf,  and  which  unite 
with  thofe  that  accompany  the  inguinal  blood- 
velTels.  The  induftry  of  late  anatomifts  has  tra- 
ced fome  of  them  even  to  the  network  of  the  tefti- 
de  itfelf. 

Dcccxvjii.  The  blood,  moved  flow'ly  and  in  a 
fmall  quantity,  brought  by  its  arteries  into  the  in- 
ner fabric  of  the  tefticle,  (dcccxiii.)  is  diftributed 
into  minute  veffels,  which  carry  their  fluids  to  the 
feminal  veffels,  although  we  are  ignorant  of  the 
manner  by  which  the  arteries  communicate  with 
thefe  tubes,  bundles  of  which  form  the  whole  fub- 
ftance  of  the  tefticle.  Thefe  are  fmall,  ferpentine, 
fomew^hat  firm,  and  have  a very  fmall  caliber  in 
proportion  to  their  membranes  j they  are  not,  how- 
ever, fo  impervious  as  to  prevent  them  from  being 
ftlled  through  the  vas  deferens.  They  are  collect- 
ed together  into  bundles,  above  tw^enty  in  number, 
feparated  by  cellular  partitions,  which  defcend 
from  the  albuginea  into  the  tefticle,  and  condud 
the  arteries  and  veins.  In  each  cell  there  is  a duct 
which  receives  the  femen  from  the  feminiferous 
veflels.  Thefe  ducts,  twenty  or  more  in  numberj 
form  a network  of  longitudinal  veffels  adhering 
to  the  albuginea,  and  inofculate  wdtll  each  other  ; 
and  readily  permit  quickfilver  to  efcape  into  the 
furrounding  cellular  fubftance.  From  this  net 
twenty  or  thirty  ducts  afeend  to  the  upper  part  of 
the  epididymis,  which  being  wonderfully  convolu- 
ted, form  as  many  vafcular  cones.  Thefe,  joined 
together  by  intermediate  cellular  fubftance,  and  ly-» 
ing  upon  each  other,  form  the  head  of  the  epididy- 
mis, and  in  that  head  foon  meet  together  into  one 
dudl  on  the  outfide  of  the  tefticle. 

Dcccxix.  This  finsrle  duct  beins^  convoluted  into 
an  infinite  numher  of  folds  and  ferpentine  flexures. 
In  a manner  not  found  in  any  other  part  of  the 

body, 


Chap.  XXVII.  MALE  GENITALS. 


4c<J  ' 


body,  and  connected  together  by  much  loofe  cel- 
lular fubftance,  and  being  collected  by  one  con- 
tinuous membrane  produced  from  the  albuginea, 
conftitutes  the  epididymis.  But  the  du6l  of  which 
the  epididymis  is  compofed,  grows  larger  as  it  de- 
fcends ; from  whence  being  reflected,  it  again  af- 
cends  along  the  pofterior  furface  of  the  tefticle,  and 
by  degrees  unfolding  its  fpiral  convolutions,  which 
are  now  much  larger,  it  gets  the  name  of  ductus 
deferens.  Almoft  always,  however,  a fmall  veffel 
feparates  fomewhere  from  the  du<5tus  deferens,  and 
afcends  along  with  the  chord,  having  an  uncertain 
termination. 

Dcccxx.  This  is  the  courfe  defcribed  by  the  fe- 
men,  moved  forwards  by  the  fluid  fuccellively 
coming  from  the  tefticle,  and  perhaps  by  the  cre- 
mafter  ; but  very  flowly,  as  we  may  conclude  from 
the  numberlefs  convolutions  of  the  epididymis,  ob- 
ftru(fLing  almoft  every  kind  of  injeftion  ; and  from 
the  length  of  time  that  is  required  to  repair  the 
femen,  after  the  feminal  veftcles  have  been  ex- 
haufted. 

Dcccxxi.  The  cylindric  du(ftus  deferens  being 
compofed  of  very  thick  fpongy  fubftance,  included 
betwixt  two  firm  membranes,  perforated  by  a very 
fmall  tube,  begins  at  the  bottom  of  the  epididymis, 
afcends  in  the  chord  of  the  fperm.atic  veffels,  pafles 
through  the  ring  of  the  abdomen  (dcccxii.)  de- 
fcends  into  the  pelvis,  applies  itfelf  to  the  bladder 
between  the  ureters,  and  there  meets  with  its  fab- 
jacent  receptacle,  which  is  called  the  veficula  femi- 
nalis,  of  which  there  are  two,  one  right  and  one 
left.  Here  the  vas  deferens  lies  on  the  inner  fide 
of  the  veficle,  as  far  as  the  proftate  gland  ; and  be- 
ing dilated  in  its  courfe,  and  bent  in  a ferpentine 
direction,  it  appears  cellular.  But  very  near  the 
proftate,  the  duct,  being  continued  from  thefe  cel- 
lular windings,  unites  with  a conical  du6t  coming 
from  the  veficle,  in  a very  acute  angle,  into  one 
C c duct, 


402 


MALE  GENITALS.  Chap.  XXVIL 


du(T,  alfo  conicalj  which  is  continued  rather  from 
the  vas  deferens,  and  penetrates  through  the  prof- 
tate  gland,  there  forms  a great  flexure,  diverges 
outwardly  at  right  angles  from  its  companion  of 
the  other  fide,  and,  becoming  contracted,  opens  in- 
to the  urethra  in  one  of  the  two  very  fmall  lateral 
orifices  of  the  tumid,  long  beaked,  hollow  protu- 
berance. By  injecting  a liquor  into  the  ductus  de- 
ferens of  a dead  fubject,  we  perceive  that  it  flows 
both  into  the  urethra  and  into  the  feminal  veficle, 
but  more  readily  into  the  former : but  in  a living 
perfon  the  femen  never  Slows  out  but  in  the  act  of 
venery  ; and  confequently  the  ductus  deferens  con- 
veys all  its  femen,  notwithftanding  the  retrograde 
angle,  to  the  feminal  veficle. 

Dcccxxii.  By  this  laft  denomination  we  under- 
ftand  a membranaceous,  firm  inteftine  lying  under 
the  bladder,  connected  with  it  by  much  cellular 
fubflance  : from  which  ten  or  more  impervious  cells 
proceed,  fome  of  which  are  alfo  ramified  and  divid- 
ed, but  which  end  in  impervious  conical  extremi- 
ties. This  inteftine,  with  a great  deal  of  firm  cel- 
lular fubftance  and  intervening  veffels,  and  perito- 
naeum lying  under  it,  is  fo  contracted,  as  to  be  col- 
lected into  a fhort  ferpentine  mafs.  Befides,  its  ex- 
ternal fabric  is  pulpy  and  thick,  and  is  fomething 
analogous  to  the  ductus  deferens..  Its  external  fab- 
ric is  wrinkled  like  the  villous  and  reticulated  coats 
of  the  biliary  veffels,  villous  with  minute  flocculi  ; 
and  is  faid  to  have  fmaU  pores  and  glands,  with 
which  I am  unacquainted,  though  it  certainly  has 
various,  and  hoUow  cells. 

Dcccxxiii.  The  liquor  depofited  in  it,,  in  the 
telticle  is  yellowifh,  thin,  and  watery and  retains 
the  fame  nature  in  the  veficle,  though  it  becomes 
there  more  vifcid  and  yellow  ; and  laftly,  in  man 
it  becomes  white,  when  it  is  mixed  with  the  liquor 
of  the  proflate.  It  has  a peculiar  hea\w  fmell,  in 
every  kind  of  animal  j and  it  is  the  heaviefl  fluid 


Chap.  XXVII.  MALE  GENITALS,  403 

in  the  body*  In  water,  part  of  it  forms  a thin, 
fwimming  pellicle,  but  the  greater  part,  which  is 
feemingly  of  a pulpy  nature,  links  to  the  bottom  ; 
and  in  the  femen  which  has  been  long  retained  by 
continent  people,  Ihining  globules  mixed  with  a 
whiter  liquor  are  ealily  feen  with  the  naked  eye., 
It  agrees  in  many  particulars  with  mucus< 

DcccxxiVi  Without  the  conveyance  of  this  into 
the  womb,  no  animal  which  is  of  two  fexes  can  be 
fecundated.  The  reafon  of  this  was  unknown,  till 
the  microfcope  fhewed,  that  in  man,  and  in  every 
other  animal,  the  feminal  liquor  is  full  of  living 
animalcules,  refembling  eels,  having  in  man  a thick 
liead,  and  a long  and  flender  but  confpicuous  tail ; 
which  are  always  found  in  healthy  femen,  from 
the  period  of  puberty ; but,  before  that  time,  and 
in  thofe  who  are  fterile  from  ficknefs,  they  are  ab^ 
fent,  and  they  are  not  found  in  any  other  animal 
fluid;  That  they  are  animalcules,  appears  evident- 
ly from  their  various  motions,  avoiding  obftacles, 
retrogreflion,  and  change  of  velocity. 

Dcccxxv.  The  real  ufe  of  thefe  animalcules  has 
been  much  doubted  ; and  we  flhall  have  another 
opportunity  of  confldering  the  received  opinion, 
that  they  are  as  it  were  the  firft  appearance  of  the 
future  animal;  To  me,  in  the  mean  time,  the  na- 
ture of  the  feminal  animalcules  feems  to  be  the 
fame  with  that  of  the  eels  in  vinegar  or  other  in- 
fufory  animals. 

Dcccxxvi.  That  the  femen  is  produced  from  the 
lymph  of  the  blood,  and  that  the  chyle  is  added  to 
the  lymph  appears  probable  from  the  difpofltion  to 
venery  quickly  fupervening  after  eating,  and  be- 
ing leflened  by  falling.  It  is  compounded  of  the 
liquor  of  the  tefticles,  and  of  the  feminal  veficles, 
which  in  fome  animals  is  more  evident,  and  of  the 
coagulable  milky  fluid  of  the  proftate  gland;  That 
liquor,  however,  only  fecundates  which  is  generat- 
ed in  the  tefticles  5 as  we  fee  from  cafcrated  ani- 
c c 2 mals. 


404 


MALE  GENITALS.  Chap.  XXVII. 


mals,  which,  though  they  have  the  feminal  veficles 
and  proftate,  are  yet  unprolific. 

Dcccxxvii.  The  feminal  fluid  is  retained  in  the 
veficles,  excepting  in  the  venereal  act  and  in  the 
illufions  of  dreams.  Being  prefent  during  that 
whole  time,  according  to  its  quantity,  it  ftimulates 
the  animal  to  venery.  But  a conliderahle  part  of 
the  femen,  and  that  the  moft  volatile  and  odorous, 
is  abforbed  into  the  blood,  and  by  its  addition  to 
it  produces  wonderful  changes.  Impregnating  the 
whole  animal  with  its  fmeU,  caufing  the  beard,  and 
hair  upon  the  pubes,  and  horns  to  grow,  changing 
the  voice  and  difpofitions.  For  thefe  do  not  hap- 
pen in  confequence  of  the  age  of  the  animal,  but 
of  the  femen,  and  never  occur  in  eunichs.  The 
growth  and  ftrengtli  of  caftrated  animals  are  di- 
miniflied  ; but  in  uncut  animals,  the  ferocity  and 
llrong  fmell,  diffufed  through  the  w'hole  fiefli,  in- 
creafes.  And  from  fome  examples  o£  anim.als,  and 
even  of  men,  it  has  evinced  a fatal  irritating  pow- 
er, by  exciting  convulfions.  Retention  of  the  femen 
feems  to  proceed  from  the  narrownefs  of  the  femi- 
nal duel,  excretory  duft,  a feirrhofity  of  the  prof- 
tate, and  other  .caufes  not  fufficiently  known.  * 

Dcccxxviii.  The  quantity  of  femen  expelled  at 
one  time  from  the  veiicles  in  man  is  but  fmall, 
efpeciaUy  if  the  abftinence  from  venery  has  been 
iiiort ; and  it  is  natural  that  it  fliould  be  but  flowly 
produced  from  fo  fmall,  and  that  a fubcutaneous 
artery.  Its  generation  is  accelerated  by  love,  by 
the  prefence  of  the  beloved  objefl ; fo  that  it  dif- 
tends  its  veffels  with  a fenfe  of  pain.  Nature  her- 
felf,  therefore,  enjoins  venery  for  the  prefervation 
of  the  human  race,  and  likewife  of  the  health  of 
every  found  man.  That  it  paffes  from  the  tefticle 
into  the  veficles,  is  fhewn  by  difeafes,  in  which  the 
duffus  deferens  being  obftruCfed,  a fweUing  of  the 
tefticle  has  enfued.  From  the  veficle  it  does  not 
efcape,  except  during  the  venereal  act. 


DCCCXXIX. 


Chap.  XXVIT.  MALE  GENITALS.  405 

Dcccxxix.  As  the  femen  is  fmall  in  quantity, 
that  it  might  be  proje^Ied  with  greater  force,  and 
to  a further  diftance,  another  humour,  which  is 
generated  by  the  proftate,  is  added  to  it.  This 
gland,  fliaped  like  a heart,  with  the  fmall  end  fore- 
moft,  furrounds  the  origin  of  the  urethra,  and  con- 
tains it,  though  moft  contiguous  to  the  upper  fur- 
face  of  the  gland.  It  is  a very  hard  and  compadl 
gland,  of  a peculiar  fabric,  not  evidently  conglom- 
erate ; it  prepares  a thick,  white,  bland,  copious 
fluid,  which  is  projected  at  the  fame  time  and  from 
the  fame  caufes  (dcccxl.)  with  the  femen  itfelf, 
into  the  excavations  at  each  fide  of  the  openings  of 
the  feminal  veficles,  through  numerous  duels,  and 
in  the  femen  its  white  colour  and  vifeidity  are  pre- 
dominant. 

The  urethra,  although  cylindrical  upon  the  whole, 
has  three  confiderable  dilatations.  The  firft  in  the 
proftate  at  the  caput  gallinaginis,  the  fecond  in  the 
bulb,  and  the  third  in  the  beginning  of  the  glans. 
Its  courfe  at  firft  is  generally  horizontal,  afterwards 
it  afeends  along  the  ofiTa  pubis,  and  in  the  male  it 
is  finally  pendulous,  except  in  the  time  of  venery. 
It  is  a continuation  of  the  nervous  coat  of  the  blad- 
der, and  is  internally  lined  with  a very  fmooth  epi- 
dermis ; between  which  and  the  nervous  coat  there 
is  cellular  fubftance. 

Dcccxxx.  But  is  was  neceflary  for  this  urethra 
to  be  firm  and  ftraight,  that  the  femen  might  be 
thrown  with  fome  force  into  the  diftant  womb  j 
therefore  it  is  furrounded  by  a triple  cavernous  bo- 
dy. The  firft,  the  proper  cavernous  body  of  the 
urethra,  begins,  as  foon  as  that  canal  has  pafled  the 
proftate,  with  a thick  origin,  almoft  like  a heart  j 
at  firft  it  lies  under  the  urethra,  but  afterwards  fur- 
rounds  it  alfo  above,  but  is  there  thinner,  and  ac- 
companies it  through  the  whole  length  of  the  pe- 
nis, till  the  lower  part  terminates  in  the  glans,  while 
the  upper  part  is  refteded  back  from  the  extremity 

of 


MALE  GENITALS.  Chap.  XXVII. 


406 

of  the  urethra,  and,  being  dilated,  returns  in  a con., 
trary  direftion  along  the  penis,  and,  being  termi- 
nated by  a broad,  thinner,  and  round  extremity,  it 
refts  upon  the  corpora  cavernofa  penis,  and  for  the 
moft  part  communicates  with  them  by  an  imperfect 
feptum.  The  fabric  of  this  body  is  cellular,  but 
lax,  and  compofed  rather  of  plates,  interwoven  like 
a net,  than  of  fibres,  and  inclofed  between  two  firm 
membranes. 

Dcccxxxi.  Into  this  cavernous  body  of  the  ure- 
thra, the  blood  is  poured  out  from  the  deep  feated 
arteries,  which  come  from  the  external  hemorrhoi- 
dals  (dcccxxxvi.)  This  is  demonftrated  by  the 
injed:ion  of  any  kind  of  fluid,  which  eafily  flows 
from  thefe  arteries  into  the  cellular  fpaces  fur- 
rounding the  urethra.  But  they  are  not  fponta- 
neoufly  turgid  with  blood,  becaufe  there  are  veins 
equally  open,  fufficient  to  carry  av^ay  the  effufed 
blood.  But  when  thefe  veins  are  coinprefled  by 
the  powers  mentioned  in  dcccxxxix.  the  blood  is 
then  retained  within  the  cellular  fpaces,  while  the 
arteries,  being  ftronger,  continue  to  pour  it  in. 
Thus  the  blood  ftagnating,  diftends  the  bulb  of  the 
urethra,  together  with  its  cavernous  body,  and  the 
glans  itfelf.  But  this  is  performed  generally  when 
the  other  cavernous  bodies  of  the  penis,  with  which 
this  of  the  urethra  has  no  communication,  are  pre- 
vioufly  diftended. 

Dcccxxxii.  The  cavernous  bodies  of  the  penis 
arife  from  the  ofia  ifehii,  almofl:  from  their  bottom, 
with  which  they  are  joined  by  a white,  cellular, 
but  very  denfe  and  firm  fubftance ; from  whence 
inclining  inwards  and  towards  each  other,  they  in- 
clofe  the  urethra,  a little  before  its  bulb,  where, 
changing  their  direction,  they  go  on  parallel,  and 
conjoined  together,  with  the  urethra  lying  below 
and  between  them,  and  terminate  in  the  glans  with 
an  acute  end,  laterally  furrounded  by  the  cavernous 
body  of  the  urethra.  They  confifl;  of  a veiw  firm 

integument, 


Chap.  XXYII.  MALE  GENITALS. 


407 

integument,  and  Ipongy  internal  flefli,  as  in  the 
urethra,  (dcccxxx.)  like  it  aifo  capable  of  being 
diftended  with  blood.  Between  thefe  cavernous 
bodies,  there  is  a middle  feptum,  compofed  of 
firm  parallel  tendinous  fibres,  growing  narrower 
downwards,  and  not  continuous  ; fo  that  the  inter- 
mediate fpaces  are  larger  and  more  numerous,  as 
they  are  more  forward  j and  a free  communication 
is  left  between  the  right  and  left  fpongy  body. 
Other  fibres  of  this  kind  run  through  the  cavernous 
bodies,  as  well  as  the  feptum,  and  are  inferted  in- 
to the  very  firm  involucrum : they  prevent  over- 
diftention  and  aneurifms  of  the  penis. 

Dcccxxxiii.  Thefe  cavernous  bodies  are  fur- 
rounded  by  much  very  fine  cellular  fubftance  ; of 
which  the  part  lying  next  the  cavernous  bodies  is 
tenfe  and  firm,  like  a membrane  j without  it  the 
cellular  fubftance  is  very  tender,  continuous  with 
that  of  the  fcrotum,  and  included  within  a thin 
fkin  without  any  fat,  and  always  the  more  tender 
the  nearer  the  fkin  it  is.  By  inflation,  it  affumes 
a beautiful  fiiky  texture.  But  the  glans  (dcccxxx.) 
is  covered  in  the  following  manner  by  the  fkin  : be- 
ing continued  from  the  penis,  and  reflecled  againft 
itfelf,  as  in  the  eyelids  ; covered  on  both  fides  with 
its  proper  cuticle,  and  filled  with  intermediate  cel- 
lular fubftance,  it  is  called  the  preputium,  and  may 
be  drawn  back,  and  laftly,  it  is  continued  forwards 
again  to  the  glans  penis,  and  is  there  changed  into 
a tender,  foft,  fpongy,  flocculent  body,  acutely  fen- 
fible,  covered  with  its  proper  cuticle,  and  with  a 
depreffed  pulpy  reticulum,  fpread  over  the  refledted 
cavernous  body  of  the  urethra,  (dcccxxx.)  and, 
finally,  continuous  with  the  membrane  of  the  ure- 
thra itfelf.  The  prepuce  is  tied  by  a double  trian- 
gular frsenulum,  by  which  the  fkin  is  joined  to  the 
cellular  involucrum  of  the  penis,  as  far  as  the  mouth 
of  the  urethra.  In  the  hollow  which  lies  under  the 
crown  of  the  glans,  and  in  that  circle  itfelf,  are 

feated 


MALE  GENITALS.  Chap.  XXVIL 


408 

feated  limple  febaceous  follicles,  v/hich  feparate  a 
liniment,  which,  from  the  nature  of  the  place,  is 
fetid,  as  in  other  parts  of  the  body  expofed  to  fric- 
tion. The  whole  penis  is  fuftained  by  a firm  cel- 
lular fubftance,  compadfed  into  a kind  of  triangular 
ligament,  which  defcends  from  the  fynchondrofis  of 
the  ofia  pubis,  and  is  continuous  with  the  denfe 
and  hard  cellular  ftratum  that  furrounds  the  caver- 
nous bodies. 

ncccxxxiv.  The  whole  human  penis  forms  a 
cylindrical  body,  deprelTed  on  the  upper  part,  of 
variable  magnitude,  whofe  ufe  is  to  be  received  into 
the  female  parts  of  generation,  and  to  carry  thither 
the  prolific  femen. 

Dcccxxxv.  Thcfe  cavernous  bodies  of  the  penis, 
during  coition,  by  the  blood  impelled  through  the 
arteries,  and  retained  in  the  veins,  become  turgid, 
diftended  and  ftilF,  and  fuftain  the  flaccid,  or  if  it 
alone  were  filled,  the  weak  urethra,  in  fuch  a man- 
ner that  the  femen  may  arrive  at  the  diftant  womb. 
This  is  demonftrated  from  the  difleclion  of  animals 
killed  in  the  acf  of  venery,  from  artificial  eredion, 
from  the  injedion  of  liquid  fubftances  into  the  vef- 
fels  of  the  penis.  It  is  produced  by  love,  the  defire 
of  enjoyment,  the  fridion  of  the  glans,  and  various 
irritations  of  the  bladder,  tefticles,  feminal  veflels, 
and  urethra,  from  urine,  from  abundance  of  good 
femen,  from  the  venereal  poifon,from  cantharides, 
whipping  with  rods,  or  nervous  convmlfion.  But 
the  caufe  of  this  diftention  is  not  yet  evident.  The 
defcription  of  the  diftribution  of  the  blood-veflels 
into  the  genital  parts  is  therefore  now  neceflary,  to 
Ciow  how  little  it  is  adapted  for  promoting  the 
caufe  tvhich  coinpreflTes  the  veins. 

Dcccxxxvi.  The  aorta  at  the  fourth  vertebra  of 
the  loins,  and  the  vena  cava  at  the  fifth,  are  didd- 
cd  ; of  thefe  the  latter  is  pofterior,  the  former  an- 
terior. The  common  iliac  branches,  before  they 
arrive  at  the  middle  interval  at  the  beginning  of 


Chap.  XXVII.  MALE  GENITALS. 


409 

the  thighs,  fend  off  inwards  and  downwards  a con- 
fiderable  artery,  called  the  hypogaftric,  which  in 
the  foetus  is  larger  than  the  femoral  artery,  and  in 
tire  adult  is  equal  to  it.  This  defcends  into  the 
pelvis,  and  divides  into  four,  five,  or  fix  principal 
branches  ; of  which  the  firfl:  is  the  iliaca  anterior, 
which  alfo  fends  branches  to  the  dura  mater  and 
cauda  equina,  upwards  to  the  loins,  and  downwards 
to  the  os  facrum.  The  next,  the  facra  lateralis, 
goes  to  the  fame  os  facrum  and  cauda  equina,  when 
it  does  not  arife  from  the  former.  The  third,  the 
iliaca  pofterior,  is  almoft  confined  to  the  glutei 
mufcles.  The  fourth,  the  ifchiadica  defcendens, 
fupplies  feveral  mufcles,  the  nerves,  and  the  leva- 
tor ani.  The  fifth,  or  the  trunk,  is  the  hsemorrhoi- 
dea  infirna  or  pudenda  communis,  which,  within 
the  pelvis  itfelf,  fends  confiderable  branches  to  the 
bladder,  and  to  the  rectum  the  middle  hsemorrhoi- 
dal,  which  anaftomofes  with  the  mefenterics  ; after 
which,  going  out  of  the  pelvis,  it  creeps  by  the  fide 
of  the  obturator,  and  gives  off  the  external  hiemor- 
rhoidals  to  the  fphincler  and  fkin  of  the  anus  : 
then  dividing,  its  internal  branch  fupplies  the  bulb 
of  the  urethra  and  the  proftate ; the  external  is 
again  divided,  and  with  one  branch  enters  deeply 
into  the  cavernous  body  of  the  penis,  and  runs 
through  its  whole  length  ; while,  the  other  branch 
often  joined  with  the  veffels  of  the  bladder,  runs 
along  the  back  of  the  penis,  and  terminates  in 
branches  fent  to  its  corpora,  and  to  the  fkin.  The 
fixth  is  the  obturatrix,  fpent  upon  the  joint  of  the 
femur  and  adjacent  mufcles.  The  laft,  the  umbil- 
ical artery,  wiU  be  defcribed  in  treating  of  the  foe- 
tus ; in  the  adult  it  fends  fome  branches-  to  the 
bladder,  from  its  thick  callous  vagina.  Sometimes 
feveral  of  thefe  arteries  arife  from  one  common 
trunk.  The  fkin  of  the  penis  and  fcrotum  have 
their  arteries  from  the  epigaftric,  from  the  crural, 
and  from  its  internal  branch.  Thefe  external  ar- 
teries 


410  MALE  GENITALS.  Chap.  XXW. 

terles  communicate  in  m.any  places  with  the  inter- 
nal. 

Dcccxxxv'ri.  The  veins,  in  general,  correfpond 
with  the  arteries.  They  often  come  off  from  the 
iliacs  in  two  trunks,  forming  a plexus  with  each 
other  ; then  the  haemorrhoidal  vein,'  returning  a- 
round  the  os  pubis,  forms  a very  large  plexus  upon 
the  proftate  gland,  wnth  the  veins  of  the  bladder 
arifmg  in  the  pelvis  : from  which  the  vena  penis 
arifes,  which  is  often  lingle,  and  is  furnilhed  with 
valves,  determining  the  return  of  the  blood  to  the 
cava.  The  external  veins  of  the  penis  and  fcrotum 
go  to  the  faphsena  and  crural,  and  communicate  in 
feveral  places  with  the  internal  veins,  more  efpecial- 
ly  at  the  balls  of  the  prepuce. 

Dcccxxxviii.  The  lymphatic  veflels  of  the  penis, 
feen  by  very  eminent  anatomifts,  are  faid  to  run 
under  the  Ikin  of  the  penis.  The  nerves,  \vhich 
are  very  numerous,  and  very  large,  and  accompany 
the  arteries  of  the  penis,  arife  from  the  great  trunk 
of  the  fciatic  nerve.  But  the  bladder,  rectum,  and 
uterus,  are  fupplied  by  the  lower  mefenteric  plex- 
us, which  arifes  from  the  middle  one,  and  defcends 
into  the  pelvis. 

iMZCcxxxix.  To  dillend  the  penis,  It  is  neceflar)'- 
that  the  veins  (dcccxxxvii.)  carryung  back  the 
blood  from  the  cavernous  bodies  of  the  penis  or  ure- 
thra, be  compreffed,  or,  at  leaft,  that  a power  be  ap- 
plied to  the  ultimate  veins,  which  open  ever)^  where 
into  the  cavernous  bodies,  hindering  them  from  ab- 
forbing  the  blood  brought  there  by  the  arteries. 
The  firft  may  be  in  fome  degree  effected  by  the  le- 
vator, drawing  up  the  proftate  and  bladder  ; but, 
from  the  analog^''  of  the  nipples  of  the  female  breaft, 
of  the  gills  of  the  peacock,  of  the  blulliing  of  the 
face  produced  by  the  paftions  of  the  mind,  and  of 
animals,  all  of  w^hich  copulate  in  the  fame  manner, 
without  any  erector  mufcle  ; of  the  erection  in  ani- 
mals totally  dift'erent  in  their  ftrufture  from  man. 


Chap.  XXVII.  MALE  GENITALS.  411 

and  efpecially  of  the  very  fudden  ereftions  in  birds  j 
from  the  very  inadion  of  the  erector  mufcles  them- 
felves  during  libidinous  erection,  and  from  their 
unfitnefs  for  compreffing  the  veins  j it  is  probable, 
that,  independently  of  the  mufcles,  the  abforption 
of  the  blood  by  the  veins  may  be  retarded,  and  that 
it  is  affected  by  the  multitude  of  deep  feated  ner- 
vous noofes,  which  being  conflricted  by  the  force 
of  pleafure,  comprefs  the  veins,  fo  that,  being  ren- 
dered narrower,  they  return  lefs  blood  to  the  trunks 
than  what  is  imported  by  the  arteries,  which  are 
not  only  free  from  any  ftrifture,  but  at  the  fame 
time,  by  the  increafe  of  the  pulfe,  are  bringing  the 
blood  more  quickly,  which  is  an  acceffory  caufe. 
But  the  caufe  of  this  convulfion  feems  to  exift  in 
the  nervous  fphinfters,  fince  the  penis  becomes 
erected,  both  from  mechanical  irritation  of  the 
nerves,  and  that  more  fubtile  irritation  caufed  by 
the  imagination. 

DcccxL.  To  a continued  and  violent  erection, 
an  expulfion  of  femen  at  laft  fucceeds,  which 
requires  much  greater  force  than  fimple  erection. 
For  the  femen  is  emitted  when  the  irritation  of  the 
nerves  is  arrived  at  its  greateft  height ; and  in  nat- 
ural venery,  when  the  cellular  fpaces  of  the  urethra, 
which  are  later  of  being  filled,  and  the  continuous 
glands  at  laft  become  turgid  with  blood,  fo  that  be- 
ing diftended  with  a large  quantity  of  warm  blood, 
they  become  ftiff,  and  therefore  the  nervous  pa- 
pillae, being  erected,  are  violently  affefted  by  the 
caufe  of  pleafure.  The  feminal  veficles  are  evacua- 
ted by  the  levator  mufcles  of  the  anus,  which  prefs 
them  againft  the  refifting  bladder,  being  excited 
either  by  voluptuous  imagination  alone,  or  by  the 
exceflive  pruritus  of  the  nerves  of  the  glans,  efpe- 
cially of  its  lower  part,  in  the  neighbourhood  of  the 
frenum.  The  femen  is  never  difcharged  along  with 
the  urine,  in  a healthy  man  ; becaufe  the  expulfion 
of  it  requires  the  bladder  to  be  fhut ; for,  while 

lax, 


VIRGIN  UTERUS.  Chap.  XX^TR. 


412 

lax,  it  affords  no  refiftance  to  the  feminal  veficles. 
The  tranfverfe  mufcles  feem  to  dilate  the  canal  of 
the  urethra  for  the  reception  of  the  femen  expreffed 
from  the  veficles. 

DCCCXLi.  Soon  afterwards,  the  fenfible  urethra 
being  irritated  by  the  femen,  the  powers  conftrict- 
ing  it  are  called  into  action.  This  is  principally  ef- 
fected by  the  accelerator,  (dccch.)  which  ftrongly 
comprefling  the  bulb  and  adjacent  part  of  the  ure- 
thra, propels  the  contents  more  fwaftly,  in  propor- 
tion as  the  bulb  exceeds  in  diameter  the  urethra. 
That  this  may  act  firmly ■,  the  fphincter  of  the  anus, 
and  therefore  alfo  that  of  the  bladder,  mult  be  con- 
tracted. The  accelerator  feems  alfo  to  be  the  prin- 
cipal mufcle  of  erection,  by  compreffmg  the  veins 
of  the  corpus  cavernofum  of  the  urethra.  At  the 
fame  time,  the  ereCtores  penis,  as  they  are  common- 
ly called,  arifing  from  the  above  tubercles  of  the 
ifchium,  being  ftrong,  and  inferted  into  the  ca- 
venious  bodies,  fupport  the  penis,  in  a direction  in- 
termediate betwixt  the  tranfverfe  and  perpendicu- 
lar. Thus  the  femen  is  projected  into  the  vagina, 
and  into  the  uterus  itfelf,  in  prolific  coition.  This 
action  is  very  violent,  and  comes  near  to  a convul- 
fion  ; whence  it  is  wonderfully  debilitating,  and 
very  much  injures  the  nervous  fyltem  principally, 
as  the  maladies  arifing  from  thence  feem  to  indi- 
cate, from  the  affection  of  the  nerves,  without  which 
the  femen  cannot  be  expelled. 


C El  A P.  XXVIII. 

VIRGIN  UTERUS. 

DCCcxLii.  ^HE  uterus  in  woman  is  feated  in  the 
I upper  part  of  the  pelvis,  wdth  the 
bladder  before,  and  the  rettum  behind  it,  without 
adhering  to  either  of  them,  and  with  its  mouth  in- 
clining 


Chap.  XXVIII.  VIRGIN  UTERUS.  413 

dining  a little  forwards.  In  the  female  adult,  it  Is 
contained  within  the  pelvis  ; but  in  the  infant,  it  rifes 
above  it.  In  women,  the  peritonaeum  defcends  from 
the  os  pubis  into  the  pelvis,  and  proceeds  for  a con* 
fiderable  way  behind  the  bladder,  to  the  bottom  of 
the  uterus.  Then  it  afcends  along  the  uterus  ; and 
a fecond  time  defcends  on  its  oppolite  fide,  applied 
to  it  as  far  as  the  vagina,  and  the  tranfverfe  portion 
of  the  uterus,  from  whence,  including  the  redum 
with  lunated  folds,  it  ceafes  to  differ  from  the  ftruc- 
ture  in  man.  But  this  fame  peritonaeum,  coming 
into  the  pelvis  from  the  iliac  veffels,  and  being 
broader  than  the  uterus,  and  adhering  to  its  fides, 
and  to  the  vagina  ; and  being  refieded  along  itfelf, 
divides  the  pelvis  into  two  regions,  the  anterior  and 
pofterior,  like  a partition,  and  is  called  the  ligamen- 
tum  latum.  It  is  accurately  conneded  with  the 
uterus,  without  any  intermediate  fat,  fo  as  to  ferve 
it  on  all  fides  as  an  external  coat.  It  does  not  hin- 
der the  uterus  from  being  totally  moveable. 

DcccxLiii.  Th^  body  of  the  uterus  is  ufuaRy  dif- 
tinguilhed  from  its  neck.  The  figure  of  the  body 
is  convex  before  and  behind,  with  a degree  of  flat- 
nefs,  with  acute  edges,  where  itsfurfaces  meet,  con- 
verging at  the  fides,  and  moderately  convex  at  the 
top.  It  has  a peculiar  fabric,  of  a clofe  compad, 
firm,  but  fom.ewhat  fucculent,  cellular  fubftance,  in 
which  we  perceive  mufcular  fibres,  efpecially  in 
puerperal  women.  They  are  flat,  and  reticularly 
interwoven  with  each  other,  fome  longitudinally 
difpofed  along  the  uterus  from  the  fundus  to  the 
os  uteri,  others  arranged  in  various  circles,  and  par- 
ticularly in  the  fundus,  and  betwixt  the  tubes,  and 
likewife  in  the  neck  near  the  mouth.  In  beafts,  the 
, uterus  is  manifeftly  mufcular  ; and  in  women,  like- 
wife, it  gives  evident  figns  of  a contradile  nature. 
Its  outer  coat  is  received  from  the  peritonaeum. 
After  repeated  examinations,  I have  not  found  any 
mucous  finufes,  branching  and  varioufly  dividing 

within 


VIRGIN  UTERUS.  Chap.  XXVIIL 


414 

within  the fabft an ce  of  theuterus,but  veinsfurround- 
ed  with  cellular  fubftance, which  do  not  collapfe.  The 
internal  membrane  of  the  uterus  is  continuous  with 
the  cuticle  ; within  the  cavity,  it  is  pulpy,  and  cov- 
* ered  with  fliort  flocculi ; in  the  cervix,  it  is  callous 
and  valvular.  The  cavity  of  the  uterus  is  fmall,  al- 
moft  triangular,  but  bounded  by  lines  convex  in- 
wardly ; in  the  remaining  part,  it  is  a comprefl'ed 
cylinder.  This  part,  which  is  called  the  cervix  uteri, 
is  cylindrical,  compreffed,  and  thick,  and  has  alfo 
a cylindric  cavity  within.  It  is  entirely  rough,  with 
callous  wrinkles,  extenuated  to  an  edge,  and  inclin- 
ed towards  the  vamna.  Thefe  recede  from  an  an- 

O 

terior  and  pofterior  line  towards  the  fides,  and  are 
joined  by  fmaller  wrinkles,  in  the  intervals  of  which 
are  mucous  linufes,  as  round  globules  are  every 
where  found  in  the  upper  part  of  the  neck  of  the 
womb,  filled  with  a very  pellucid  liquor,  differing 
both  in  number  and  magnitude.  It  is  not  uncom- 
mon for  the  uterus  to  be  divided  by  a middle  pro- 
jecting line.  I’he  cervix  is  terminated  by  the  os 
internum  uteri,  having  a ti'anfverfe  flit,  furrounded 
with  tumid  lips,  drawn  out  into  the  vagina,  and  re- 
ceived within  its  blind  extremity,  projecting  into  it 
obliquely  and  forwards.  It  is  full  of  mucus,  and 
has  mucous  fmufes  in  its  tumid  edges. 

DcccxLiv.  The  triangular  part  of  the  uterus  fends 
out,  from  its  lateral  angles,  canals,  folded  together 
by  means  of  cellular  fubftance,  growing  gradually 
broader,  and,  again  a little  contracted  towards  the 
extremity  : their  direction  is  at  firft  tranfverfe  to- 
wards the  ovarium,  and  afterwards  defeending,  but 
with  fome  variation  : they  are  termed  the  Fallopi- 
an tubes.  Their  external  membrane  is  from  the  pe- 
ritonseum  ; for  they  are  included  within  tlie  dupli- 
cature  of  the  broad  lig^ament : their  internal  mem- 
brane  is  wrinkled  almoft  reticularly,  mucous,  and  is 
extended  to  a greater  length,  in  tlie  form  of  fpread 
fringes,  folded  longitudinally,  which  crown  the  ori- 


Chap.  XXVIII.  VIRGIN  UTERUS. 


415 

fice  of  the  ovarium,  and  are  conneded  to  the  ovary. 
Betwixt  the  two  membranes,  is  fome  fpongy  cellu- 
lar fubftance,  of  a more  Gender  texture  than  in  the 
vas  deferens.  They  ufuaUy  contain  mucus,  the 
origin  of  which  is  not  known.  There  are  alfo  a 
great  number  of  veffels  interpofed,  and  perhaps  fome 
mufcular  Gbres,  but  the  latter  are  more  obfcure. 
They  are  fupported  by  a proper  fold  of  the  pe- 
ritonaeum, which  proceeds  from  the  broad  liga- 
ment. 

DcccxLv.  The  ovaries  are  tranfverfely  Gtuated  in 
the  fame  broad  ligament,  included  in  its  duplica- 
ture  behind  the  tubes,  and  conjoined  to  thefe  tubes 
by  a peculiar  expanGon  of  the  broad  ligament, 
which  is  long  enough  to  allow  them  a free  motion. 
They  are  of  an  oblong  figure,  comprelled  on  each 
fide  ; their  unconneifed  edge  is  convex,  and  femi- 
elliptical  ; but  that  which  is  connefted  with  the 
ligament  is  ftraight.  Their  peritonaeal  membrane 
is  thick,  and  almoft  cartilaginous.  Their  fabric 
very  much  refembles  that  of  the  uterus  itfelf  ; be- 
ing clofe,  white,  and  cellular,  and  without  fat.  The 
margin  of  the  broad  ligament,  where  it  recedes 
from  the  uterus,  becoming  thicker,  to  fuftain  the 
ovary,  has  fomething  of  a folid  fubfiance,  refem- 
bling  a ligament,  but  is  not  hoUow,  or  a true  ca- 
nal. 

DcccxLvi.  In  the  ovary  even  of  a young  girl, 
there  are  round  veficles,  confifiing  of  a pretty  ftrong 
pulpy  membrane,  and  connected  every  where  to 
the  ovarium  by  cellular  threads,  which  are  filled 
with  coaguiable  lymph  ; uncertain  in  their  num- 
ber, fifteen  or  more  being  found  in  one  ovary  5 nor 
uniform  in  their  fize.  They  are  remarkable  bo- 
dies, being  found  very  widely  diffufed  through  all 
animals,  even  in  thofe  which  have  but  one  fex. 

DcccxLvii.  Laftly,  the  uterus  fends  forwards, 
from  the  fame  lateral  angles  of  its  triangular  body, 
a fafciculus,  compofed  of  long  cellular  fibres  and 

veffels. 


416  \1RGIN  UTERUS.  Chap.  XX\TIL 

veffels,  which,  becoming  fmaller  in  its  progrefs, 
goes  out  of  the  pelvis  through  the  ring  of  the  ab- 
domen (dcccxii.)  into  the  groin,  where  it  fplits 
into  branches,  and  feparates  into  fmall  veffels,  which 
communicate  with  the  epigaftrics.  Has  it  alfo  long 
fibres  propagated  from  the  uterus  itfelf  ? I have 
not  feen  them  fufficiently  diftincfly. 

DcccxLviii.  The  arteries  of  the  uterus  are  from 
the  hypogaftrics  ; a conliderable  branch  of  which 
the  uterine,  like  the  loweft  to  the  bladder  in  men, 
arifes  from  the  umbilical  trunk,  or  immediately  be- 
low that  trunk.  It  goes  to  the  lower  part  of  the 
uterus,  almoft  at  the  termination  of  its  neck,  giwng 
branches  to  the  uterus,  bladder,  and  rectum,  and 
afeending  upwards,  it  fends  tranfverfe  inflected 
branches  to  the  uterus,  makes  numerous  anoftamo- 
fes  with  the  fpermatics,  and  often  gives  arteries  to 
the  tube  itfelf.  Another  plexus  of  branches  tends 
downwards  to  the  vagina,  running  along  it  a con- 
fiderable  way,  although  there  is  alfo  a proper  vagi- 
nal artery  originating  likewife  in  the  pelvis,  and 
fometimes  acceffory  branches  from  the  mefocolic. 
There  are  alfo  feminal  veffels  which  have  the  fame 
origin  as  in  men,  and  defeend  with  a pampiniform 
plexus  over  the  pfoas  mufcle  into  the  pelvis,  and  di- 
vide into  two  plexufes.  The  pofterior  goes  to  the 
ovary  itfelf,  with  many  twifted  furculi  diftributed 
throusfh  its  fubftance  and  among  the  ova.  The  ante- 
rior  both  fupplies  the  tube,  and  defeends  to  the  ute- 
rus, in  which  it  is  divided  into  winding  branches  up- 
wards and  downwards,  fome  going  to  the  bladder. 
Another  artery,  the  middle  hsemorrhoidal,  from 
the  trunk  of  the  pudenda  communis,  accompanies 
the  vagina  a confiderable  way  forwards,  to  which, 
and  to  the  bladder  and  reefum,  it  is  diftributed. 
Moreover,  the  beginning  of  the  vagina  and  the  cli- 
toris, have  arteries  from  the  external  haemorrhoidal, 
and  the  clitoris,  like  the  penis,  has  both  deep  feated 


Chap.  XXVIII.  VIRGIN  UTERUS. 


417 

and  fuperficlal  arteries,  alfo  inofculating  with  a 
branch  from  the  bladder. 

DcccxLix;  The  uterine  veins  oft  the  whole  cor- 
refpond  with  the  arteries,  originating  from  the 
trunks  of  the  hypogaftrics  ; they  are  both  internal 
as  the  uterine,  the  vaginal,  and  middle  hemorrhoi- 
dal^  and  external  as  the  circumflex,  and  thofe  of 
the  clitoriSi  But  they  form  a remarkable  plexus 
on  each  fide,  which  occupies  the  fides  of  the  vagi- 
na below  the  clitoris.  Below  that,  it  is  joined  in^ 
to  a continued  plexus  with  its  companion  on  the 
Other  fide.  A plexus  alfo  from  the  external  he- 
morrhoidal and  vefical  velfels,  goes  to  the  clitoris, 
as  in  men  to  the  penis.  They  have  no  valves,  ex- 
cept a few  in  the  fpermatics,  which  alfo,  in  a very 
large  bundle,  go  to  the  ovarium,  and  the  alse  vef- 
pertilionis. 

DcccL.  Within  the  uterus  itfelf  the  arteries  ter- 
minate in  exhaling  branches  on  its  internal  furface. 
In  the  puerperal  Rate  they  are  elongated  into  pen- 
dulous tubes.  Thus  the'  veins  of  the  uterus  become 
at  that  time  very  large  finufes  ; for  they  are  enor- 
moufly  enlarged,  and  open  with  very  large  mouths 
into  the  cavity  of  the  uterus. 

DcccLi.  Lymphatic  veffels  are  found  in  the  ute- 
rus of  brutesj  and  in  women  more  rarely,  though 
by  very  eminent  anatomifts. 

DcccLii.  The  nerves  are  fupplied  from  the  loweft 
mefocolic  plexus,  united  wdth  thofe  of  the  facrum, 
and  fending  large  branches  to  the  bladder,  womb, 
and  reftum  ; befides  which,  fome  pafs  through  the 
‘broad  ligament  to  the  ovarium,  and  others  from 
the  nerve  that  goes  with  the  veffels  to  the  clitoris, 
arifing  from  the  fciatic  trunk.  But  the  ovary  has 
alfo  its  proper  nerves  from  the  renal  plexus,  fimi- 
lar  to  thofe  which  go  to  the  teflicles  of  the  male. 
Thus  all  thefe  organs,  from  the  great  number  of 
their  nerves,  are  extremely  fenfible. 

Dd 


DCCCLIII, 


VIRGIN  UTERUS.  Chap.  XX^TH, 


418 

DcccLiii.  What  we  have  hitherto  defcribed  is 
common  to  all  ages  of  the  female  ; but  about  the 
13th  years  or  fomewhat  later,  neai'ly  at  the  fame 
time  when  femen  begins  to  be  form.ed  in  the  male, 
a confiderable  change  aifo  takes  place  in  the  female. 
For,  at  this  time,  the  whole  mafs  of  blood  in  the 
female  begins  to  circulate  with  an  increafed  force, 
the  breads  fwell,  the  pubes  becomes  covered  ; and 
at  the  fame  time  the  menfes  begin  to  flow,  by  a 
common  law  of  nature  ; although  in  different  coun- 
tries, the  time  and  quantity  of  blood  difcharged  is 
different. 

DcccLiv.  This  difcharge  is  preceded  by  various 
fymptoms  in  the  loins,  heavy  pains,  fometimes  like 
colic  pains,  with  an  increafed  pulfe,  headachs  and 
cutaneous  puftules,  and  a white  fluid  commonly 
flows  from  the  uterus.  For  now  the  fleecy  vefl'els 
of  the  uterus,  which  have  hitherto  depofited  into 
the  uterus  a milky  fluid,  of  a very  white  colour  in 
the  foetus,  and  in  young  girls  ferous,  now  begin  to 
be  turgid  with  blood  ; and  at  lafl;  to  pour  out  the 
red  cruor  itfelf  into  the  cavity  of  the  uterus.  This 
continues  fome  days,  while,  in  the  mean  time,  the 
flrft  troublefome  fymptoms  abate,  and  the  orifices 
of  the  uterine  veflels  again  gradually  contracfing, 
diftil  only  a little  ferous  moifture  as  before.  But 
at  uncertain  intervals  in  young  girls,  gradually, 
however,  fhortening  to  the  end  of  the  fourth  week, 
the  fame  pains  return,  the  fame  flow  of  blood  takes 
place,  and  this  period  is  obferved  to  about  the  50th 
year  ; though  the  diet,  country,  and  conftitution, 
have  much  influence  in  this  refpecf.  Pregnancy 
commmonly  produces  a ceflation  of  the  menftrual 
difcharge. 

EcccLv.  That  this  blood  is  difcharged  from  the 
veflels  of  the  uterus  itfelf,  is  demonftrated  by  acfual 
infpedion  of  women  who  have  died  during  their 
courfes  ; of  living  women,  in  whom  the  uterus 
being  inverted,  has  diflilled  the  blood  from  the  os 

internum : 


Chap.  XXVIIL  VIRGIN  UTERUS. 


419 

internum  : and  of  others,  in  whom,  from  obflmc- 
tion  of  the  menfes,  the  uterus  has  been  filled  with 
concreted  blood  ; and  by  comparing  the  nature  of 
the  uterus  itfelf,  replete  with  foft  veffels,  and  fpon- 
gy  with  the  thin,  by  no  means  villous,  and  callous 
vagina.  Obfervation  alfo  fhews,  that  this  is  good 
blood  in  an  healthy  and  clean  woman.  However, 
there  is  nothing  to  prevent  the  blood  from  being 
difcharged  through  the  vagina,  when  the  uterus  is 
obftruHed,  as  in  other  inftances  it  is  through  the 
in'teftinum  rectum,  and  laftly  through  the  remoteft 
parts  of  the  body. 

DcccLvi.  Since  no  animal  certainly  menftruates 
in  the  fame  manner  as  the  human  fpecies,  (although 
fome  animals  diftil  blood  from  their  genitals,  in  the 
feafon  of  their  annual  venery)  and  fince  the  body  of 
the  male  is  free  from  this  periodical  difcharge,  the 
caufe  of  this  hemorrhagy,  peculiar  to  the  female  fex 
of  the  human  fpecies,  has  been  an  objedl  of  inquiry 
in  all  ages.  From  the  remoteft  periods,  it  has  been 
afcribed  to  the  attraction  of  the  moon,  which  is 
known  to  raife  the  tides ; by  others,  to  a fliarp  fti- 
mulating  fluid  fecreted  in  the  female  parts,  alfo  the 
caufe  of  the  venereal  appetite.  But  its  being  caufed 
by  the  moon  is  difproved,  fince  there  is  not  a day 
in  which  there  are  not  many  women  ftibjefted  to 
this  evacuation,  and  there  are  not  fewer  in  the  de- 
creafe  than  the  inereafe  of  the  moon.  There  is  no 
fuch  thing  as  any  ferment  near  the  uterus,  but  every 
thing  is  bland  and  mucous  ; and  venery,  which  ex- 
pels all  thofe  juices,  neither  increafes  nor  lelfens  the 
menftrual  flux ; and  women  deny,  that,  during  the 
time  of  their  menfes,  they  have  any  increafed  defire 
of  venery,  many  of  them  at  that  time  being  rather 
affected  by  pain  and  languor  5 and  the  feat  of  vene- 
real pleafure  is  rather  in  the  entrance-of  the  puden- 
dum than  in  the  uterus,  from  which  laft  the  menfes 
flow.  Laftly,  that  the  menftrual  blood  is  forced 
out  by  fome  caufe  exciting  the  motion  of  the  blood 
D D 2 againft 


420 


VIRGIN  UTERUS.  Chap.  XXVin. 


againft  tte  veffels,  appears  from  hence,  that,  when 
retained,  it  has  been  known  to  break  through  all 
the  other  organs  of  the  body,  where  no  ferments 
were  acting,  the  veins  being  even  ruptured ; nor  is 
the  effedl  of  the  retained  blood  confined  to  thofe 
parts  which  pour  out  the  venereal  humour. 

DCCCLvii.  Nature  has,  in  general,  given  women 
a fofter  body,  lefs  elaftic  folids,  fmaller  mufcles,. 
with  a greater  quantity  of  fat  interpofed  betwixt 
their  fibres,  and  ilenderer  bones,  with  fmaller  pro- 
cefl'es.  Moreover,  the  pelvis  of  the  female  is,  in  all 
its  dimenfions,  larger  ; the  offa  ilia  more  diftant 
from  each  other  ; and  the  os  facrum  turned  more 
backwards  from  the  bones  of  the  pubes,  while  the 
offa  ifchii  are  feparated  by  a longer  line  ; but  above 
all,  the  angles  in  which  the  bones  of  the  pubes 
meet  is  much  larger  : which  differences  are  con- 
firmed by  the  obfervations  of  the  greateft  anato- 
mifts  ; and  from  neceffity  itfelf,  which  requires  a 
greater  fpace  for  the  greater  number  of  vifcera  in 
the  pelvis.  Moreover,  the  arteries  fupplying  the 
uterus  are  very  large,  more  fo  than  in  men  ; and 
their  caliber  is  larger  in  proportion  to  their  coats,  and 
they  are  more  lax  in  proportion  to  the  veins  : but 
the  veins  are,  in  proportion,  lefs  ample  in  the  men,^ 
and  of  a more  firm  texture  than  in  other  parts  of 
the  body.  From  hence  it  follows,  in  the  firft  place, 
that,  in  women,  the  blood  is  brought  to  the  womb 
in  greater  quantity,  and  more  quickly,  through  lax 
and  ample  arteries ; and,  in  the  fecond  place,  that,, 
on  account  of  the  rigidity  and  narrownefs  of  the- 
veins,  it  returns  with  difficulty  from  the  uterus, 
and  diftends  its  veffels. 

DcccLiK.  The  female  infant,  when  firft  born,  has 
fmall  lower  extremities ; and  the  greater  part  of 
the  blood  of  the  iliac  arteries  goes  to  the  umbilicals, 
a fmall  portion  only  enters  the  pelvis.  Hence  the 
pelvis  is  fmall,  and  little  concave ; and  the  bladder 
and  uterus  itfelf,  with  the  ovaries,  rife  above  the 

pelvis. 


Chap.  XXVm.  VIRGIN  UTERUS. 


421 


pelvis.  But,  when  the  foetus  is  born,  and  the  um- 
bilical artery  is  tied,  all  the  blood  of  the  iliac  arte- 
yy  defcends  into  the  lower  limbs  and  pelvis,  which 
grow  larger,  and  the  pelvis  becomes  deeper  and 
wider  ; fo  that  by  degrees,  the  womb  and  bladder 
fink  into  its  cavity,  and  are  not  fo  much  compreffed 
by  the  intefiines  and  peritonseum,  when  the  abdo- 
minal mufcles  central  the  lower  parts  of  the  belly. 
Then,  when  the  grov/th  is  completed,  or  nearly  fo, 
the  arteries  of  the  uterus,  and  of  the  pelvis  in  gen- 
eral, which  in  the  foetus  were  very  fmall,  have  be- 
come very  large,  and  are  eafily  injefted  with  wax  j 
and  all  things  are  fo  changed,  that  the  hemorrhoi- 
dal artery  now  forms  the  trunk  of  the  hypogaftric 
(dcccxxxvi.)  as  formeiiy  the  umbilical  had  done. 
More  blood,  therefore,  at  this  time  goes  into  the 
uterus,  vagina,  and  clitoris,  than  formerly. 

DcccLx.  At  the  time  when  the  growth  of  the  bo- 
dy has  almoft  ceafed,  and  a large  quantity  of  blood 
is  prepared  in  found  vifeera  and  in  healthy  confti- 
tutions,  plethora  takes  place  in  both  lexes  of  the 
human  fpecies.  In  the  male,  it  vents  itfelf  fre- 
quently by  the  noftrils,  from  the  exhaling  veffels 
of  the  pituitary  membrane  (ccccnviii.)  being  di- 
lated to  fo  great  a degree,  as  to  pour  out  the  red 
blood,  and  now  the  femen  firfl:  begins  to  be  fecre- 
ted,  and  the  beard  to  grow.  But  in  the  female, 
the  fame  plethora  finds  a more  eafy  paffage,  be- 
caufe  the  very  weight  of  the  blood  carries  it  down- 
wards, and  becaufe  the  uterine  veffels,  now  much 
enlarged,  being  placed  in  a lax  fituation  in  the  fuc- 
culent  and  foft  cellular  fubftance  of  the  uterus,  and 
being  therefore  very  extenfile  and  exhaling  by  very 
foft  flocculi,  open  into  the  empty  uterus,  and  the 
blood  finds  almoft  a more  eafy  paffage  that  way,  than 
into  the  correfponding  veins  ; while  in  the  fame  fe- 
males, the  arteries  of  the  head  are  firmer  and 
fmaller  in  proportion.  The  return  of  the  blood 
is  alfo  retarded,  both  becaufe  the  flexures  of  the 

arteries 


422 


VIRGIN  UTERUS.  Chap.  XXVIII, 

arteries,  from  the  increafed  afflux  of  the  blood,  be-f 
come  more  ferpentine  and  fitter  for  retarding  the 
m.otion  of  the  blood,  and  bccaufe  it  now  returns 
with  difficulty  through  the  "eins.  The  blood  is, 
therefore,  firil  coliecled  in  the  veiTels  of  the  uterus, 
which  at  this  time,  according-  to  difi'eclions,  are 
turgid  ; then  in  the  arteries  of  the  loins  and  in  the 
aorta  itfelf ; now  when  the  heart  fends  a new  tor- 
rent of  blood  into  the  veffels  already  diftended,  its 
force  is  at  laft  propagated  to  the  ferous  veffels  of 
the  uterus,  fo  that  they  difcil  at  firft  a copious  warm 
mucus,  then  red  ferum,  and  laftly  pure  blood.  The 
fame  determination  of  the  blood  to  the  genital  parts, 
forces  out  the  hitherto  latent  hairs,  ihcreafes  the 
bulk  of  the  clitoris,  dilates  the  cavernous  plexufes 
of  the  vagina,  and  excites  the  appetite  towards  ve- 
nery,  Accordingly,  the  quantity  of  the  mcnftrual 
diicharge  is  increafed,  and  its  firft  appearance  haf- 
tened  by  every  thing  that  either  increafes  the  quan- 
tity of  blood  in  general,  or  determines  it  particu- 
larly to  the  uterus  ; fuch  as  joy,  defire,  pediluvia, 
a full  diet,  warm  climate,  and  lively  temperament 
of  body.  It  is  diminiffied  by  thofe  things  which 
diirnniflr  plethora  and  the  motion  of  the  blood,  as 
want,  grief,  cold  atmofphere,  inactivity  and  pre- 
ceding difeafes. 

DcccLxi.  When  fix  or  eight  ounces  of  blood 
have  been  thus  evacuated,  the  unloaded  arteries 
now  exert  their  elaftic  force  as  all  arteries  do,  and 
their  diameters  being  contracted,  they  only  tranf- 
mit  a thin  fluid  as  at  firft.  But  the  quantity  of 
blood  wffiich  the  uterus  difcharged,  being  repro- 
duced by  the  fame  caufes,  it  is  again  excreted 
through  thefe  fame  paffages,  rather  than  througii 
any  other.  Nor  is  it  neceifary  to  inquire,  why  this 
period  is  nearly  menftrual ; for  this  depends  upon 
the  proportion  which  fubfifts  between  the  quantity 
and  miomentum  of  the  blood  coUcched,  and  tlie  re- 
fiftance  of  the  uterus,  which  v'ill  at  laft  uraduahv 


Chap.  XXVIH.  VIRGIN  UTERUS. 


423 

yield.  Therefore  this  difcharge  of  blood  returns 
Iboner  and  does  not  wait  for'  the  interval  of  a 
month,  whenever  a greater  quantity  of  blood  is 
determined  to  the  uterus  in  plethoric  or  libidinous 
women.  They  ceafe  entirely  to  flow,  when  the 
uterus,  like  all  the  other  folid  parts  of  the  body,  has 
acquired  fo  great  a degree  of  hardnefs,  as  cannot 
be  overcome  by  the  force  of  the  heart  propelling 
the  arterial  blood.  This  hardnefs  in  the  uterus, 
in  the  arteries  and  ovaries,  is  fhewn  by  the  knife 
and  by  injections.  Animals  in  general  have  no 
menfes  ; on  account  of  their  uteri  being  membra- 
nous rather  than  flefhy,  and  if  the  firmnefs  of  their 
veifels,  which  is  fo  great,  that  in  thefe  animals  no 
hemorrhage,  either  from  the  noftrils,  or  any  other 
part,  ever  occurs.  In  men  they  do  not  occur, 
becaufe  in  their  pelvis  there  is  no  fpongy  organ  fit 
for  retaining  the  blood  ; and  becaufe  the  arteries 
of  the  pelvis  are  both  harder  and  fmaller  in  pro- 
portion than  the  veins,  and  thus  the  impetus  of  the 
blood  is  turned  aflde  into  the  lower  extremities,  of 
which  in  men,  the  growth  is  greater,  as  that  of  the 
pelvis  is  lefs. 

DcccLxii.  Why  do  the  breafts  fwell  at  the  fame 
time  ? Their  fabric  in  many  refpeCts  is  analogous  to 
that  of  the  uterus  ; as  appears  from  the  fecretion  of 
the  milk  in  the  breafts,  which  fticceeds  the  birth  of 
the  foetus,  and  which  increafes  or  diminifties  in  pro- 
portion as  the  lochial  flux  diminiflies  or  increafes  ; 
from  the  fimilitude  of  the  ferous  liquor,  found  in 
the  uterus,  to  the  thin  whitifli  milk,  in  thofe,  who 
are  not  laClefeent,  which  is  very  apparent  in  ani- 
mals ; and  from  the  erection  of  the  nipples  by 
friction,  analogous  to  the  erection  of  the  clitoris. 
Therefore,  the  fame  caufes  which  diftend  the  vef- 
fels  of  the  uterus,  Ijkewife  determine  the  blood 
more  plentifully  to  the  breafts  j the  confequence  of 
which  is  an  increafe  of  the  conglomerate  gland  of 
the  breaft,  and  of  the  furrounding  fat. 


CHAR 


4?4 


CONCEPTION. 


Chap.  XXIX, 


CHAP.  XXIX. 

CONCEPTION, 

DcccLxiii.  TE  now  enter  upon  a ver^'  difficult 

V V ffibject  ; to  inveftigate  what  in- 
ternal changes  take  place  in  woman,  when  the 
germination  of  the  life  of  a new  being  begins  udth- 
in  her,  whom,  in  proper  time,  fhe  is  to  bring  forth. 
We  Ihall  relate,  in  the  firft  place,  therefore,  thofe 
things  which  obfervation  has  proved  ; and  then 
fliall  add  thofe  hypothefes  by  which  learned  men 
have  endeavoured  to  fupply  whatever  is  not  learnt 
from  experience.  How  few  things  are  afcertain- 
ed  on  this  fubject,  and  how  difficult  they  are  to 
be  afcertained,  I have  learned  too  much  by  expe- 
rience. 

DcccLxiv.  That  fome  light  may  appear  amidft 
this  darknefs,  we  fliall  begin  with  the  mofl;  Ample 
animals,  and  afterwards  notice  what  nature  has  add- 
ed in  others  wffiofe  fabric  is  more  compounded. 
The  fmallcft  animals  then,  w'hich  have  very  few  or 
no  limbs,  very  little  diflinclion  of  parts,  very  fliort 
period  of  life,  the  vital  funftions  both  few  and  very 
limilar  to  each  other  ; thefe  animals  bring  forth 
young  ones  like  themfclves,  with  no  diftincHon  of 
iexes,  all  of  them  being  fruitful,  and  none  fecun- 
dating the  reft.  Some  of  them  exclude  their  young 
whom  they  have  conceived  in  their  bodies,  through 
fome  opening  in  their  bodies  ; from  others,  fome 
limbs  fall  oft',  which  are  completed  into  animals  of 
a kind  Amilar  to  thofe  from  -which  they  have  fallen. 
This  kdnd  of  generation  is  extended  very  widely, 
and  comprehends  the  greater  part  of  animal  life. 

DcccLxv.  The  next,  wdiich  are  a little  more  com- 
pounded, all  parturiate  ; yet  in  fuch  a manner,  that 
in  their  bodies  is  generated  a certain  particle,  dil- 

fimilai' 


Chap.  XXIX. 


CONCEPTION. 


425 

iimilar  to  the  whole  animal,  and  contained  in  fome 
involucra,  within  v/hich  lies  the  animalcule  that  is 
afterwards  to  become  fimilar  to  that  within  which 
it  is  produced  ; thefe  are  called  eggs.  A great  part 
of  thefe  animals  is  immoveable. 

DCCCLxvi.  The  animals  which  follow,  which  are 
not  indeed  numerous,  have  both  eggs  and  alfo  male 
femen  ; fo  that  both  fexes  are  joined  in  the  fame  in- 
dividual. By  the  m.ale  femen  we  underhand  that 
with  which  it  is  neceiTary  for  the  eggs  to  be  fprink- 
led,  in  order  to  become  prolific,  although  alone  it 
never  becomes  a new  animal.  In  this  clafs,  there- 
fore, a juice  is  prepared  by  its  own  proper  organs, 
which  is  poured  on  the  eggs  generated  in  like  man- 
ner, in  proper,  but  different  organs. 

DcccLxvii.  Thofe  animals  are  much  more  numer- 
ous which  have  both  a male  juice  and  female  eggs  ; 
and  yet  are  not  capable  of  fecundating  themfelves, 
but  ftand  in  need  of  real  venery.  For  of  this  kind 
two  individuals  concur  in  the  work  of  fecundation, 
in  fuch  a manner,  that  each  impregnates  the  other 
with  its  male  organs,  and  reciprocally  has  its  fe^ 
jnale  organs  impregnated  by  the  male  parts  of  the 
other. 

DcccLxviii,  And  now  the  nature  of  animals  ap- 
proaches  nearer  and  nearer  to  that  of  the  human 
race  ; amongft  the  individuals  of  which,  though  in 
other  refpefts  fimilar,  fome  have  only  male  organs, 
;and  thefe  males  fprinkle  their  femen  on  the  fe^ 
male  eggs  of  others.  Many  cold  blooded  animals 
affufe  their  feed  upon  the  eggs  after  they  are  ex-, 
eluded  from  the  body  of  the  mother.  Warm  ank 
mals  injeef  their  femen  into  the  very  uterus  of  the 
female.  But  now,  whether  eggs  be  generated  with- 
in the  body  of  the  female,  and  the  feetufes  be  pro-, 
duced  inclofed  in  coverings,  or  whether  the  female 
carry  the  live  foetus  fo  long  in  its  uterus,  until  it 
produce  them  without  any  involucrum  ; the  dif- 
ference between  thefe  oviparous  and  viviparous  an- 
imals 


426  CONCEPTION.  Chap.  XXIX. 

imals  is  fo  fmall,  that  in  the  fame  clafs,  and  in  the 
fame  genus,  fome  animals  lay  <iggs,  and  others  Ih  e 
fcetufes  ; and,  laftly,  the  fame  animal  fometimes 
lays  eggs,  and  fometimes  brings  forth  live  young. 

DcccLxix.  From  this  review  of  animals  it  ap- 
pears, that  all  of  them  are  produced  from  an  ani- 
mal hmilar  to  themfelves ; many  of  them  from  a 
part  of  it  fimilar  to  the  whole  j others  from  an  egg 
of  a peculiar  ftrucfure ; but  that  all  thefe  do  not 
hand  in  need  of  male  femen.  Laftly,  the  locomo- 
tive and  more  lively  animals,  having  a compound 
ftrufhire,  only  are  endowed  with  a double  fyftem 
for  generation ; and  the  difference  of  fexes  feems 
to  be  added  for  the  bond  of  focial  life,  and  for  the 
prefervation  of  a lefs  numerous  progeny. 

DcccLxx.  To  this  effufion  of  the  male  juice  into 
the  female  ors^ans,  both  fexes  are  excited  bv  the 
moft  vehement  delires  : the  male  indeed  moft  ftrong- 
ly ; the  female  being  always  ready  to  fuffer  the  ve- 
nereal congrefs,  it  behoves  the  male  to  be  animated 
with  a defire  of  venery,  when  he  has  abundance 
of  good  and  prolific  femen.  Therefore,  this  cir- 
cumhance  itfelf  is  the  gneateff  caufe  of  venereal 
dehre  in  him  ; but  in  females,  of  the  brute  kind 
efpecially,  it  is  a certain  degree  of  inflammation  in 
tlie  vagina,  which  excites  an  intolerable  itching. 

DCCCLXxi.  But  nature  has  added,  for  combining 
the  energy  of  both,  in  women  and  in  quadrupeds, 
to  the  uterus,  a vagina  or  round  membranous  canal, 
very  dilatable,  which,  embracing  the  mouth  of  the 
uterus,  (dcccxi.iii.)  defcends  downwards,  and  then 
downw’ards  and  forwards,  lying  under  the  bladder, 
add  refling  upon  the  rectum  to  which  it  adheres, 
and,  laftly,  opens  under  the  urethra  with  an  orifice 
a little  contracted.  This  orifice,  in  the  foetus  and 
in  virgins,  is  protected  from  the  action  of  the  air  or 
water,  by  a remarkable  valvular  fold,  denominated 
the  hymen,  formed  of  the  fkin  and  cuticle  of 
the  vagina,  probably  for  fome  moral  purpofe,  as 

amongft 

O 


Chap.  XXIX. 


CONCEPTION. 


427 

amongft  all  the  animals  I have  examined,  it  exifts 
only  in  the  human  fpecies.  It  would  be  circubr, 
if  it  were  not  incomplete  under  the  urethra  and 
even  there  it  is  not  always  deficient ; toward  the 
anus  it  is  broader.  Being  gradually  worn  away 
by  copulation,  and  lacerated,  it  at  laft  difappears. 
The  caruncles,  which  are  called  myrtiformes,  are 
partly  the  remains  of  the  lacerated  hymen,  and 
partly  the  indurated  extremities  of  the  columnse  of 
the  vagina ; and,  laftly,  the  valves  of  the  mucous 
lacunae  hardened  into  a kind  of  fiefh. 

DCCCLXXii.  The  fabric  of  the  vagina  in  women 
is  cutaneous,  and  is  compofed  of  a firm  callous  cuti- 
cle, and  a thick,  white,  nervous  fkin,  in  which,  more 
efpecially  at  its  extremity,  fleflry  fibres  appear.  Its 
internal  furface  is,  in  a great  meafiire,  rough  with 
callous  verrucas,  which,  though  hard,  are  fenfible, 
and  with  inclined  laminae,terminated  by  a projecting 
edge,pointing  downwards,  and  arrangedfo  that  they 
are  collefted  into  two  principal  columns,  ftudded 
as  it  were  with  thefe  verrucae,  of  which  the  upper- 
moft  and  largefi:  is  extended  under  the  urethra,  and 
the  loweft  is  incumbent  on  the  anus.  From  each 
of  thefe,  a valvular  feries  of  fmaller  papillae,  va- 
rioufly  infleded  into  arches,  is  continued  till  they 
mutually  meet  on  both  fides.  This  fabric  feems  to 
be  defigned  for  the  purpofes  of  enjoyment,  and  for 
facilitating  its  expanfion.  It  is  furnifhed  with  a 
peculiar  mucus,  from  finufes  fituated  all  over  it, 
but  more  efpecially  in  its  pofterior  and  fmoother 
fide. 

DcccLxxiii.  At  the  entrance  of  the  vagina  are 
prefixed  two  cutaneous  appendages,  called  nymphae, 
continued  from  the  cutis  of  the  clitoris,  and  from 
its  glans  itfelf,  full  of  intermediate  cellular  fub- 
ftance,  of  a diftendible  fabric,  jagged  and  furnifhed 
on  both  fides  with  febaceous  glands,  fuch  as  are 
alfo  found  in  the  folds  of  the  prepuce  of  the  clitoris, 
'llieir  chief  ufe,  it  is  fuppofed,  is  to  dired  the  urine, 

which 


CONCEPTION. 


428 


Chap,  XXIX, 


which  flows  betwixt  them  from  the  urethra,  fo  aa 
to  turn  it  off  from  the  body,  which  office  is  attended 
with  a certain  ereclion  of  the  nymphae.  Thefe 
membranes  defcend  from  a cutaneous  arch  fur- 
rounding the  clitoris,  which  is  a part  extremely 
fenfible,  and  wonderfully  prurient,  and,  like  the 
penis,  is  compofed  of  two  cavernous  bodies,  arifing 
from  the  fame  bones,  and  joined  together,  but  vnth- 
out  including  any  urethra.  It  is  furnifhed  with 
blood-veflels,  nerves,  and  levator  mufcles,  and  a 
ligament  fent  down  from  the  fynchondrofis  of  the 
olfa  pubis,  analogous,  to  thofe  in  men  : and  in  like 
manner  from  venery,  the  clitoris  grows  turgid  and 
ere£l,  but  lefs  in  raodeft  women  j but  from  friction 
always. 

DcccLxxiv.  The  mufcle,  termed  oftii  vaginze 
conftriftor,  arifes  on  each  lide  from  the  fphincter 
of  the  anus,  and  being  increafed  by  an  acceflion 
from  the  as  ifehium,  covers  the  vafcular  plexus, 
and  proceeds  broadly  fonvards,  along  the  begin- 
ning of  the  labia  externa,  and  is  inferred  into  the 
crura  ditoridis  ; it  feems  to  comprefs  the  lateral 
plexufes  of  the  vagina,  and  to  retard  the  return  of 
the  venous  blood  in  both  ways.  The  tranfverfe 
mufcle  of  the  urethra,  and  the  bundle  from  the 
fphincter  inferred  into  it,  have  the  fame  fituation  as 
in  men. 

DCCCLxxv.  The  female  being  invited  either  by 
moral  love,  or  the  delire  of  pleafure,  admits  the 
male,  whofe  penis  being  introduced  into  the  vagi- 
na, is  rubbed  againft  its  fides,  until  the  male  femen 
h ejefted  and  thrown  into  the  uterus.  Thus,  as 
we  have  obfeiwed  of  the  male,  (dcccxl.)  the  fric- 
tion of  parts  fo  tender  and  exquilitely  fenfible,  ex- 
cites a convulfive  conftriction  of  all  the  parts  fur- 
rounding the  vagina.  By  thefe  means,  the  return 
of  the  venous  blood  being  fuppreffed,  the  clitoris, 
both  the  nymphze,  and  the  plexus  furrounding  al- 
mofl  all  the  vagina,  become  turgid,  more  efpcciaily 


Chap.  XXIX.  CONCEPTION.  429 

in  libidinous  women  ; the  pleafure  is  raifed  to  the 
higheft  pitch  : and,  laftly,  though  not  always^  or  in 
all  women,  there  is  expelled,  by  mufcular  force, 
{dccccxxiv.)  a mucous  lubricating  liquor  of  va- 
rious origin.  The  principal  fources  of  this  are, 
in  the  firft  place,  in  the  entrance  of  the  urethra, 
where  large  mucous  finufes  are  placed  in  the  tumid 
extremity  of  this  uriniferous  canal.  Then,  at  the 
fides  of  the  urethra,  in  the  bottom  of  the  linufes 
which  are  formed  by  the  membranous  valves  being 
concave  upwards,  two  or  three  large  mucous  finuf. 
es  penetrate  into  the  fubftance  of  the  urethra  itfel£ 
Laftly,  at  the  fides  of  the  vagina,  betwixt  the  bot- 
toms of  the  nymphse  and  the  hymen,  there  is  one 
opening,  on  each  fide,  from  a very  long  dudl ; 
which,  defcending  towards  the  anus  receives  mu- 
cus from  fmall  follicles. 

DcccLxxvi.  But,  by  the  fame  aflion  which  in- 
creafes  the  pleafure  to  the  higheft  degree,  and, 
therefore,  caufes  a conflux  of  blood  to  the  whole 
genital  fyftem  of  the  female,  (dlxiii.)  a much  more 
important  change  is  produced  in  the  internal  parts 
of  the  female  : for,  when  the  hot  femen  of  the  male 
penetrates  into  the  fenfible  cavity  of  the  uterus, 
which  is  itfelf  turgid  and  heated  with  influent  blood, 
the  Fallopian  tubes  at  the  fame  time  fwell,  being 
very  full  of  diftended  veflels,  creeping  betwixt  their 
two  coats,  and  now  filled  with  a very  great  quan- 
tity of  blood.  In  this  ftate,  thefe  tubes  become  red 
and  rigid,  and  the  fringed  mouth  of  the  tube  af- 
cends,  and  is  applied  to  the  ovarium.  All  thefe 
changes  are  confirmed  by  difleflions  of  women,  and 
other  animals,  and  by  morbid  cafes. 

DCCCLXxvii.  But,  in  a female  of  ripe  years,  the 
ovary  is  extremely  turgid,  with  a lymphatic  coagu- 
iable  fluid,  with  which  the  veficles  are  diftended. 
In  a prolific  copulation,  fome  one  of  the  riper  of 
thefe  veficles  burfts,  and  opens  with  a manifeft  cleft, 
and  at  length  effufes  a clot  of  blood.  Within  this 

veficle. 


CONCEPTION. 


Chap.  XXIX. 


43.6 

velicle,  after  copulation,  a kind  of  flelli  is  formed, 
at  firft  flocculent,  then  granulous,  and  like  a con- 
glomerate gland,  confiiling  of  many  acini  joined  to- 
gether by  cellular  fubftance  ; which,  by  degrees, 
becoming  larger  and  harder,  fills  the  whole  cavity 
of  the  veficle,  and  is  indurated  till  it  acquire  a fcir- 
rhous  appearance,  in  which,  for  a long  time,  a cleft, 
or  the  veftage  of  one,  remains.  This  is  the  corpus 
iuteum,  common  to  all  warm  blooded  quadrupeds, 
in  which  fome  late  anatomifts  have  aflerted,  that 
there  is  a fluid  before  defloration  ; which,  however 
experience  does  not  admit,  fince  there  is  no  corpus 
Iuteum  at  that  age.  Nor  is  the  veficle,  which  be- 
comes the  human  ovum,  contained  in  the  corpus  as 
in  a calyx. 

DcccLxxviii.  Moreover,  in  a prolific  congrefs, 
the  tube,  comprefling  the  ovarium,  is  fuppofed  to 
exprefs  through  a fifl'ure  in  the  outer  membrane,  a 
mature  ovulum,  and  to  abforb  it,  and  then  to  tranf- 
mit  it  to  the  uterus  by  a periftaltic  contraction, 
which  begins  from  the  firft  point  of  contact,  and 
gradually  forces  the  ovulum  towards  the  uterus, 
as  is  very  manifeft  in  animals.  The  truth  of  this 
is  certainly  fupported  by  the  fiffure  produced  in 
the  ovarium  after  conception  ; by  foetufes  being 
certainly  found  in  quadrupeds  and  in  women,  both 
in  the  ovarium  and  in  the  tube  ; and  by  the  anal- 
ogy of  birds,  in  which  the  defeent  of  the  o\'um 
from  the  ovarium  is  very  manifeft.  Yet  we  muft 
acknowledge,  that  a true  ovum  was  never  found, 
vdth  certainty,  in  quadrupeds,  unlefs  after  a long 
time.  It  is  probable,  that  at  the  time  of  concep- 
tion, the  true  ovum  being  almoft  fluid,  very  foft 
and  pellucid,  cannot  be  diftinguiflied  from  the  mu- 
cus with  which  the  tube  is  filled ; like-.\  ife,  that 
it  is  very  fmall,  on  account  of  the  narrownefs  of 
the  tube.  The  veficle  itfelf  which  was  in  the 
ovary,  remains  fixed  in  it,  and  becomes  the  covering 
of  the  corpus  Iuteum.  But  the  accounts  of  ova, 

faid 


Chap.  XXIX.  CONCEPTION.  431 

faid  to  have  fallen  from  women  during  the 
days,  are  not  certain,  and  are  contradicted  by  the 
fmallnefs  of  the  foetus  obferved  many  days  after 
conception ; by  the  fhape  which  it  was  lirft  ob= 
ferved  to  have,  which  is  always  oblong,  and  in 
brutes  even  cylindrical ; and  likewife  by  the  linali- 
nefs  of  the  tube. 

DGCcLxxix.  Thefe  things  are  performed  with 
pleafure  to  the  future  mother,  and  not  without  a 
peculiar  fenfation  of  internal  motion  in  the  tube, 
and  of  a tendency  to  faint.  Neither  is  the  place 
of  conception  in  the  uterus,  into  which  accurate 
experiments  Ihow  that  the  male  femen  reach- 
es. For  the  power  of  the  male  femen  fecundates 
the  ovum  in  the  ovarium  itfelf,  as  is  proved  by 
the  foetufes  being  found  in  the  ovaries  and  tubes  5 
by  the  analogy  of  birds,  in  which,  by  copulation, 
one  egg  indeed  falls  into  the  uterus,  but  many  are 
fecundated  at  once  in  the  ovarium.  Nor  is  this 
inconfiftent  with  the  fmall  quantity  of  the  male 
femen,  or  its  fluggifh  nature,  which,  by  eminent 
anatomifts,  has  been  thought  unadapted  for  per- 
forming fuch  a journey.  For  it  is  certain,  that  tlie 
male  femen  has  filled  the  tubes  themfelves  after  re- 
cent impregnation,  both  in  women  and  other  ani- 
mals. 

DcccLxxx.  The  uterus  Indeed,  certainly  in  ani- 
mals, and  in  women  probably,  is  clofed  after  con- 
ception, left  the  very  fmall  ovum,  together  with 
the  hope  of  the  new  progeny,  fliould  perifli.  At 
that  time  the  new  mother  fuffers  many  difagreeable 
affeflions,  which  probably  arife  from  the  abforp- 
tion  of  the  fubputrid  and  fubalkaline  male  femen. 
Conception,  almoft  like  the  fwallowing  fome  rancid 
egg,  caufes  naufea,  efpecially  of  flefti  meat,  vom- 
iting, the  eruption  of  fome  puftules,  and  pains  in  the 
teeth.  The  greater  inconveniences  I afcribe  to 
the  fwelling  of  the  uterus,  compreffing  the  vifcera 


43^  CONCEPTION.  Chap.  XXIX. 

of  the  abdomen,  and  to  the  retention  of  the  men^ 
fes. 

DCCCLXxxi.  What  we  have  hitherto  hated,  can 
certainly  be  confirmed  or  corrected  by  the  teftimo- 
ny  of  our  fenfes.  W hat  follows  is  more  conjectural, 
and  more  difficult,  on  account  of  the  paucity  of  ex- 
periments, and  their  little  agreement  with  each 
other.  And,  in  the  firfl  place,  it  is  a difficult  quef- 
tion,  from  whence  do  the  rudiments  of  the  new 
animal  proceed  ? Are  they  derived  from  both  pa- 
rents, and  mixed  into  one  animal  by  a conjunction 
of  feminal  matter  coming  from  the  whole  body  J 
as  indeed  there  is  a refemblance  of  the  foetus  to  both 
parents  in  animals,  but  efpeciaUy  in  plants,  as  con- 
firmed by  numerous  experiments,  and  as  the  dif- 
eafes  of  parents  are  propagated  to  their  children. 
But  no  femen  has  ever  been  obfcrved  with  certain- 
ty in  females ; and  innumerable  examples  of  ani- 
mals fliow,  that  the  fpecies  may  be  propagated  with- 
out any  mixture  of  feeds.  Laflly,  the  refemblance 
to  the  father  feems  only  to  fhow,  that  in  the  male 
femen  there  is  fome  power,  which  can  influence  the 
form  of  the  foft  fubftance  of  the  very  minute  em- 
bry-o,  jufl  as  the  fame  power  adds  length  to  the  pel- 
vis in  the  body  itfelf,  dilates  the  larynx,  and  caufes 
the  horns  to  grow. 

DCccnxxxiT.  To  the  father  fome  hare  attribu- 
ted every  thing  ; chiefly  after  the  feminal  worms, 
now  fo  wellknowm,  were  firfl:  obferved  in  the  male 
femen  by  the  help  of  the  microfcope,  which  are  ob- 
ferved, with  truth,  to  agree  in  figure  with  the  form 
of  the  firfl:  embryos  of  all  animals.  But  thefe  ani- 
malcules are  not  proportionate  to  the  number  of 
the  fcetufes,  and  are  not  perpetual  in  the  different 
tribes  of  animals ; and  they  have  too  great  a re- 
femblance to  thofe  animalcules  that  are  every  where 
produced  in  other  juices,  which,  though  always  te- 
nacious of  their  owm  genus,  are  never  found  to  grow 

up 


Chap.  XXIX. 


CONCEPTION. 


433 

up  into  a totally  different  kind  of  animal,  poffeding 
limbs. 

DcccJLXxxili.  Again,  other  anatomills,  not  lefs 
celebrated  or  lefs  worthy  of  credit,  have  taught  that 
the  foetus  exifted  in  the  mother  and  maternal  ova- 
ry ; that  the  male  femen  excites  it  into  a more  ac- 
tive life,  and  likewife  influences  it  varioufly,  but  that 
it  finds  it  already  exifting  and  prefent.  For  yolks 
are  manifeftly  found  in  the  female  ovary,  even  al- 
though they  have  not  been  fubjecfed  to  any  male 
influence.  But  the  yolk  is  an  appendix  to  the  in- 
teftine  of  the  chick  ; and  derives  its  arteries  from 
the  mefenteric  artery,  and  the'  membrane  of  the 
yolk  is  continued  from  the  nervous  membrane  of 
the  intefline,  which  is  continuous  with  the  fkin  of 
the  animal.  In  the  hen,  therefore,  the  foetus  feems 
to  be  prefent  along  with  the  yolk,  which  is  a part 
of  it,  and  receives  veflels  from  it.  Laftly,  the  ana- 
logy of  nature  fliows,  that  many  animals  generate 
eggs  without  any  connection  with  a male  of  the 
fame  fpecies,  but  that  no  male  animal  is  ever  pro- 
lific without  a female.  There  is  a continued  pro- 
greflion  from  the  female  quadruped  to  the  ovipa- 
rous, and  from  that  to  the  non-oviparous.  But  the 
old  animal  produces  the  new  one  from  part  of  it- 
felf.  It  is  therefore  certain,  that  the  male  is  an  ap- 
pendage to  that  fex  which  produces  the  foetus  from 
its  own  body ; which  addition  is  neceffary  in  feme 
tribes  of  animals,  but  in  the  greateft  number,  and 
moft  fruitful,  may  be  wanted.  Nor  can  any  kind 
of  ingrafting  be  admitted  with  any  degree  of  pro- 
bability, by  which  the  dilated  navel  of  the  male- 
born  animal  fhouid  cohere  with  the  vefTels  of  the 
female.  For  this  navel  is  much  too  fmall  at  the 
time  when  the  yolk  is  of  confiderable  fize  ; nor 
could  the  very  fmall  umbilical  arteries  be  applied 
to  the  very  large  yolk  with  any  hope  of  a continu- 
ance of  the  circulation,- 
E e 


DCCCLXXXIV. 


CONCEP'riON. 


Cbiap.  XXIX. 


434 

DccCLXXxiv.  Thus  luUcIi  concerning  the  mate- 
rials. But  there  is  as  mucli  difficulty  concerning 
the  trieans  by  which  the  rude  and  ffiapelefs  mafs  of 
the  firft  embryo  is  fafhioned  into  the  beautiful  fhape 
of  the  hunaan  body.  We  readily  reject  fuch  caufes 
as  the  fortuitous  concourfe  of  atoms,  the  blind  at- 
tradlions  of  nutritive  particles,  and  the  action  of 
ferments  in confcious  of  their  effects.  The  foul  is 
certainly  unequal  to  the  talk  of  producing  fuch  a 
beautiful  fabric ; and  internal  moulds,  of  v.diich  I 
never  could  conceive  any  clear  idea,  are  to  be  re- 
ferred to  thofe  hypothefes  which  the  defire  of  ex- 
plaining thofe  things,  of  which  we  are  unwillingly 
ignorant,  has  produced. 

DccGLXxxv.  To  me,  indeed,  the  tell  of  experi- 
ment feems  to  coincide  with  thofe  things  which  the 
mind  itfelf  forefecs  will  arife  from  their  own  caufes. 
For  hence,  indeed,  it  appears  to  me  certain,  that  the 
beautiful  ftrucfture  of  animals,  fo  various,  that  it  is 
always  perfectly  adapted  to  the  proper  and  diftinct 
habits  and  functions  and  manner  of  life  of  each  j 
calculated  by  rules  more  perfect  than  thofe  of  hu- 
man geometry,  and  molt  evidently  accommodated 
to  forefeen  purpofes,  in  the  eye,  the  ear,  and  the 
hand,  and  finally,  every  where ; can  be  aferibed  to 
no  caufe  below'  the  infinite  wifdom  of  the  Creator. 
Again,  the  more  frequently,  and  the  more  minute- 
ly, we  obferve  the  long  feries  of  increafe  through 
which  the  fliapelefs  embryo  is  brought  to  the  per- 
fection neceffary  for  animal  life,  the  more  certainly 
does  it  appear,  that  thofe  things,  which  are  obferv- 
ed  in  the  more  perfect  foetus,  exifted  in  the  tender 
embryo,  although  the  lituation,  figure,  and  compo- 
fition,  feem  at  firft  exceedingly  different  from  wdiat 
they  appear  at  laft ; for  an  unwearied  and  labori- 
ous patience  difeovers  the  intermediate  degrees  by 
which  the  fituation,  figure,  and  fymmetry,  are  in- 
fenfibly  correefed.  Even  the  tranfparency  of  the 
primary  feetus  alone  conceals  many  things,  w'hich 


Chap.  XXIX.  CONCEPTION.  435 

the  colour  aftei'vcards  added  does  not  generate,  but 
renders  manifeft  to  the  eye.  And  it  fufiiciently  ap- 
pears that  thofe  parts,  which  eminent  anatornilts 
have  fuppofed  to  be  generated  at  a later  period,  and 
to  be  added  to  the  primeval  ones,  were  connate 
with  thefe,,  though  fmall,  foft,  and  colourlefs. 

DcccLxxxvi.  It  does  not  feem  improbable,  that 
the  embryo,  lying  dormant  during  a long  period, 
neither  increafes,  nor  is  agitated,  except  by  a very 
gentle  motion  of  the  humours,  which  we  may  fup- 
pofe  to  ofcillate  from  the  heart  into  the  neighbour- 
ing arteries,  and  from  thefe  back  again  into  the 
heart.  But  it  is  alfo  probable,  that  the  ftimulus  of 
the  male  femen  excites  the  heart  of  the  foetus  to 
greater  contraflions ; fo  that  it  infenlibly  evolves 
the  complicated  vefl'els  of  the  reft  of  the  body  by 
the  impulfe  of  the  fluid,  and  propagates  vital  mo- 
tion through  all  the  canals  of  the  animal  em.bryo ; 
more  quickly  into  fome  parts,  and  more  flowly  into 
others  ; and  that  from  thence  it  happens,  that  fome 
parts  of  the  body  of  the  animal  feem  to  be  produc- 
ed very  early,  and  others  to  fupervene  afterwards  ; 
and  laftiy,  that  fome  do  not  fhew  themfelves  until  a 
long  time  after  birth,  as  the  veficles  of  the  ovaries, 
the  veffcls  of  the  male  tefticles,  the  teeth,  hairs  of 
the  beard,  and  horns  of  animals.  In  aU  animals, 
heat  aflifts  this  evolution ; in  the  more  Ample  ones, 
Vv^hofe  vefl'els  are  few,  and  lefs  complicated  in  the 
Variety  of  their  origin  j it  alone  effe&  it. 

Dccci.xxxvii.  Of  the  objecftions  which  are  ufu- 
ally  brought,  fome  are  not  true,  as  the  difference  of 
ftruclure  caufed  by  nsevi ; others  feem  to  belong 
to  caufes  depending  on  fome  accident,  fuch  as  moil 
inftances  of  monfters  ; fome  to  the  increafe  of  fome 
particular  parts,  occaAoned  by  the  powers  of  the 
male  femen  ; fome  to  the  cellular  texture  varioufly 
relaxed,  fo  that  it  feems  to  form  new  parts  ; fome  to 
indurated  juices.  Although  it  is  not  eafy  to  explain 
every  thing  mechanically,  yet  we  ought  to  remeni- 
E E 2 ber. 


CONCEPTION. 


Chap.  XXIN. 


436 

ber,  tbat  if  indeed  the  new  animal  actually,  and  ac- 
cording to  obfervation,  exifts  in  the  egg,  thofe  diffi- 
culties which  are  made  cannot  overturn  things 
which  have  been  truly  demonftrated,  although  per- 
haps foine  things  may  remain,  to  which,  in  the  pre- 
lent infancy  of  human  knowledge,  we  cannot  yet 
give  a fatisfaclory  anfwer. 

DcccLXXxviii.  Some  days  after  the  human  ovum 
is  brought  dov/n  into  the  uterus,  \fe  become  more 
lenlible  of  its  changes.  The  ovum  itfelf  fends  out, 
from  every  part  of  the  furface  of  its  membrane  hith- 
erto fmooth,  foft  branchy  flocculi,  which  adhere 
to  and  iiiofculate  with  the  exhalinsf  and  abforbins; 
fiocculi  of  the  uterus  (dcccxliii.)  This  adhelion. 
takes  place  in  every  part  of  the  uterus  ; but  chiefly 
in  that  thick  part  which  lies  between  the  tubes, 
and  is  commonly  called  the  fundus  uteri.  Thus, 
the  thin  ferous  humour  of  the  uterus,  oroceedinar 
from  its  arterial  villi,  is  received  into  the  flender 
venous  veflels  of  the  otnim,  and  nouriflies  it  togeth- 
er with  the  foetus-  Before  adhefion,  it  is  either 
nourifned  by  its  proper  fluid,  or  by  abforption,  if 
indeed  there  is  a time  when  it  does  not  adhere. 

DcccLxxxix.  At  this  time,  in  the  ovum,  there 
are  contained  a great  proportion  of  a watery  fluid, 
coagulable  by  heat  or  alcohol,  and  limpid,  and  the 
foetus,  which  is  long  invifible,  as  I have  never  obferv- 
cd  it  before  the  1 7th  day,  at  firfl:  a lhapelefs  mafs,con- 
fifting  of  mere  mucus,  and  then  cylindrical.  When 
now  fome  diflindtion  of  parts  fucceeds,  it  has  a very 
great  head,  a final!  body,  no  limbs,  and  is  fixed  by 
a flat  ample  navel  to  the  obtufe  end  of  the  ovum. 

Dcccxc.  From  this  minutenefs  the  o%nim  increafes 
in  fize,  and  alfo  the  foetus,  but  in  unequal  propor- 
tions ; for  while  the  arterial  ferum  is  conveyed  by 
pafifages,  gradually  more  open,  into  the  veflels  of  the 
ovum,  the  foetus  itfelf  grows  the  fafteft,  to  which 
the  greatefl;  part  of  the  nourifliment  feems  to  pafs 

through 


Chap.  XXIX. 


CONCEPTION. 


437 

through  the  very  large  umbilical  vein.  At  the  fame 
time,  the  ovum  itfelf  alfo  grows,  but  flower,  fo  that 
the  proportion  of  the  ovum,  and  the  waters  which 
it  includes,  to  the  foetus,  is  perpetually  diminifliing. 
The  flocculi  of  the  ovum  gradually  diminifli  and 
occupy  a fmaller  portion  of  the  ovum,  and  are  in- 
fenflbly  fpread  over  with  a continuous  membrane, 
and  only  thofe  which  fprout  out  from  the  obtufe 
end  of  the  ovum  increafe,  and  are  by  degrees  form- 
ed into  a round  circumfcribed  placenta. 

Dcccxci.  Such  is  the  appearance  of  the  ovum  in 
the  fecond  month  ; and  after  that  period,  it  chan- 
ges only  in  bulk.  That  portion  of  the  ovum,  in  its 
upper  part,  next  the  uterus,  making  about  a third 
of  its  whole  bulk,  conflfts  of  a round,  flat,  fuccu- 
lent,  fibrous,  tuberous  and  perfectly  vafcular  difc, 
changed  into  equal  and  fimilar  tubercles,  accurate- 
ly, and  often  infeparably  connected,  generally  with 
the  uppermoft  part  of  the  uterus  remarkable  for  its 
large  veflTels,  by  thin  cellular  fubftance  without  fat 
collefting  the  veflels,  both  generally,  but  chiefly  in  , 
the  circumference  of  the  greateft  circle,  and  alfo  by 
the  exhaling  arteries  of  the  uterus,  anfwering  to 
the  veins  of  the  placenta,  and  by  the  arteries  of  the 
placenta,  inofculating  with  the  large  veins  of  the 
uterus.  There,  in  the  furface  common  to  the  ute- 
rus and  placenta,  a communication  exifts,  by  which 
the  uterus  tranfmits  to  the  foetus,  both  that  ferous 
liquor  not  unlike  milk,  and  laftly,  as  it  feems,  blood 
itfelf.  This  communication  of  fluids  between  the 
uterus  and  placenta,  feems  to  be  demonftrated  by 
the  fuppreflion  of  the  menfes  in  pregnant  women, 
whofe  blood  muft  be  turned  into  another  channel ; 
from  the  lofs  of  blood  which  follows  from  the  fep- 
aration  of  the  placenta,  efpecially  in  a mifcarriage  ; 
and  from  the  blood  of  the  foetus  being  exhaufled 
by  haemorrhagies  from  the  mother  ; from  haeinor- 
rhagies  that  enfue  from  the  unfecured  navel-ftring, 
while  the  placenta  remains  in  the  uterus,  killing 

the 


CONCEPTION. 


438 


Chap.  XXIX, 


the  mother  ; and,  laftly,  from  the  paffage  of  water, 
quickfilver,  tailow,  or  v/ax,  from  the  uterine  arte- 
ries of  the  mother  into  the  veffels  of  the  placenta, 
as  obferved,  and  lately  confirmed  by  eminent  anjt- 
omifts.  But  that  it  is  blood  which  is  fent  into  the 
foetus,  is  evinced  by  the  magnitude  of  the  finufes 
of  the  uterus  and  placenta  •,  the  diameter  of  the 
ferpentine  arteries  of  the  uterus ; the  haemorrhagy 
that  follows  the  feparation,  even  the  moll  gentle, 
of  the  placenta,  and  efpecially  by  the  motion  of  the 
blood,  which,  in  a foetus  deftitute  of  a heart,  could 
only  be  given  to  the  humours  of  the  foetus  by  the 
blood  of  the  mother. 

Dcccxcn.  Ihe  remaining  part  of  the  body  of  the 
ovum,  and  likewife  the  convex  furface  of  the  pla- 
centa, are  covered  by  an  external  m.einbrane,  which 
is  villous,  fiocculent,  reticulated,  porous,  cafily  lac- 
erable,  and  vafcular,  refembling  a fine  placenta,  and 
is  called  the  chorion.  This  alfo  is  connected  to  the 
fiocculent  and  very  fimiiar  but  fofter  furface  of  the 
uterus,  by  veffels  fmaller  than  thofe  of  the  placen- 
ta, but  mjnifeftly  inofculated  from  the  chorion  in- 
to the  veffels  of  the  uterus. 

Dcccxciii.  Under  the  chorion  lies  a continuous 
white,  opaque,  and  firm  membrane,  not  vafcular, 
which  does  not  cover  the  part  of  the  placenta  con- 
tiguous to  the  uterus,  but  its  concave  furface  con- 
tiguous to  the  foetus.  It  coheres  by  cellular  tex- 
ture both  with  the  chorion  and  amnios.  The 
moft  limple  name  we  can  give  it,  is  the  middle 
membrane. 

Dcccxciv.  The  innermoft  coat  of  the  foetus,  the 
amnios,  is  a watery  pellucid  membrane,  veiw  rarely 
liaving  any  confpicuous  veffels,  which,  however,  I 
have  obferved  even  in  the  human  fubjecd  ; extreme- 
ly fmooth,  and  in  all  parts  alike ; alfo  extended 
under  the  placenta  along  with  the  former,  and 
every  where  in  contact  with  the  waters.  If  there 
be  more  foetufes  than  one,  either  in  woman  or 

in 


Chap.  XXIX.  CONCEPTION.  439 

in  any  other  female,  each  of  them  has  its  proper 
amnios. 

Dcccxcv.  The  nourifhment  of  the  fetns  from  the 
beginning  to  the  end  of  the  conception,  is  without 
doubt  conveyed  through  the  umbilical  vein.  This 
gathering  its  roots  from  the  exhaling  vefTels  of  the 
uterus,  (dcccliv.)  and  from  the  umbilical  artery, 
with  which  it  is  manifeftly  continuous,  and  form- 
ing venous  linufes  under  the  furface  of  the  placen- 
ta, unites  into  a large  trunk,  which  being  twifted 
in  various  folds,  but  lefs  than  its  cprrefppnding  ar- 
teries, and  being  of  fufScient  length  to  allow  of  a 
free  motion  j furrounded  with  cellular  fubftance 
full  of  mucus ; feparated  by  three  partitions,  and  by 
the  membrane  which  is  continued  from  the  amnios, 
but  firmer,  and  known  by  the  name  of  the  um- 
bilical rope  ; and  fwelling  into  feveral  knots,  en- 
ters the  navel  between  diverging  arches  of  the  (kin 
and  abdominal  mufcles,  and  proceeding  to  a pro- 
per finus  of  the  liver,  (ocxcii.)  fends  the  fmaller 
portion  of  its  blood  through  the  ductus  venofus, 
which  is  fmaU  and  feated  in  the  pofterior  foffa  of 
the  liver,  to  the  vena  cava  ; and  tranfmits  to  the 
heart  the  greater  part  through  the  large  hepatic 
branches  which  conftantly  arife  from  its  fulcus, 
and  remain  even  in  the  adult,  (ncxcv.)  and 
through  the  branches  of  the  cava,  (dcxcvii.)  con- 
tinuous with  thefe.  The  finus  of  the  vena  porto- 
rum,  or  left  branch,  is  alfp  a part  of  the  umbilical 
vein,  and  its  branches  bring  the  blood  from  the 
placenta  to  the  cava,  while  the  right  branch  alone 
(ncxcv.)  carries  the  mefenteric  and  fplenic  blood 
through  the  liver. 

Dcccxcvi.  But  this  is  not  the  only  ufe  of  the  pla- 
centa ; for  the  foetus  fends  great  part  of  its  blood 
to  the  placenta,  through  twp  very  large  umbilical 
arteries,  which  are  the  continuation  of  the  aorta  ; 
and  after  giving  off  flender  feinorals,  and  very  fmall 
arteries  into  the  pelvis,  they  afcend  refle<Ted  along 


440 


CONCEPTION. 


Chap.  XXIX. 


the  bladder,  furrounded  by  the  cellular  plate  of  the 
peritonaeum,  and  fome  fibres  feparated  from  the 
bladder  and  urachus,  and  on  the  outfide  of  the  pe- 
ritonaeum enter  into  the  umbilical  cord,  in  which, 
alternately  ftraight  and  contorted,  veith  various 
windings,  fomcwhat  fliarper  than  thofe  of  the  vein 
around  which  they  play,  they  arrive  at  the  placen- 
ta, whofe  fubflance  is  entirely  made  up  of  their 
branches,  and  the  correfponding  veins,  and  lubri- 
cous cellular  fubftance  accompanying  both  vefTels  ; 
fo  that  the  acini  themfelves,  confpicuous  in  the 
placenta,  are  convolutions  of  vefTels.  This  blood 
leems  to  pafs  out  through  the  arterial  vefTels  of  the 
placenta  into  the  bibulous  veins  of  the  uterus,  fo  that 
after  undergoing  the  action  of  the  lungs  of  the 
mother,  it  returns  ameliorated  to  the  foetus  : For 
what  other  reafon  can  be  affigned  for  fuch  large  ar- 
teries, which  carry  off  above  a third  part  of  the  blood 
of  the  foetus  ? 

Dcccxcvii.  Is  the  foetus  alfo  nouriflied  by  the 
mouth  ? Does  it  drink  from  the  cavity  of  the  amniv.)S, 
the  lymphatic  lubricating  liquor,  which  is  coagu- 
lable,  unlefs  when  putrid,  in  which  the  fmtus  fwims, 
and  whofe  origin  is  not  fufliciently  knovm  ? Is  this 
opinion  confrmed  by  the  analogy  of  chickens, 
which  are  necefiarily  nouriflred  from  the  contents 
of  the  egg  only  ; by  the  abfence  of  a navel-ftring  in 
fome  feetufes  ; by  the  meconium  filling  the  large, 
and  part  of  the  fmaii  inteftines  ; by  the  liquor 
found  in  the  flomach  of  the  feetufes  of  birds,  and 
even  of  the  human  fpecies,  fimilar  to  that  which 
fills  the  amnios  ; by  the  proportionable  decreafe  of 
the  liquor  amnii,  to  the  growth  of  tire  foetus  ; by  co- 
agulated fibres,  found  continued  from  the  amnios, 
through  the  mouth  and  gullet,  into  the  ftomach  of 
the  foetus  ; by  hairs  and  true  faeces  being  found  in 
the  ftomach  of  the  feetufes  of  quadrupeds  ; by  the 
open  mouth  of  the  foetus,  which  we  have  certainly 
obferved  : the  gaping  of  the  chicken,  fwimmingin 
this  liquor,  and  its  attemnts  as  if  to  fwallow  it  ? 

Yv'hat 


441 


Chap.  XXIX.  CONCEPTION. 

What  are  the  fources  of  this  lymph  of  the  amnios  ? 
Does  it  tranfiide  through  the  invifible  velTels  of  the 
amnios  ? Is  it  tranfmitted  to  it  through  certain  pores 
from  the  fucculent  chorion,  which  is  itfelf  fupplied 
from  the  uterus  ? On  every  point,  numberlefs  diili- 
culties  occur  ; but  it  feems  more  probable,  that  this 
liquor  is  nutritious,  efpecially  in  the  early  ftages  of 
the  foetus,  and  that  it  is  derived  from  the  uterus. 

Dcccxcviii.  The  excrements  of  the  foetus  are  col- 
lected during  that  whole  time  in  fmall  quantity,  on 
account  of  the  great  tenuity  of  the  nutritious  fluid, 
percolated  through  the  very  fmall  veflels  of  the 
uterus.  I frequently  obferve,  that  the  bladder  is  al- 
' moft  empty  in  the  foetus.  However,  there  is  gen- 
erally fome  quantity  of  urine,  collected  in  the  large 
and  very  long  urinary  bladder.  But  in  a great  por- 
tion of  the  inteftines,  there  is  collected  a green 
pulp,  poffibiy  the  remains  of  the  exhaling  juices ; 
for  I have  feen  a flmilar  fubftance  in  other  cavities, 
that  are  filled  with  exhaling  juices,  and  in  the  vagi- 
nal coat  of  the  tefiicle. 

Dcccxcix.  Is  there,  then,  no  allantois  ? fince  it  is 
certain,  that  from  the  top  of  the  bladder  the  ura- 
chus pafles  out,  which  is  a tender  canal,  at  firft 
broad,  covered  by  the  longitudinal  fibres  of  the 
bladder  as  with  a capfule ; and  afterwards,  when 
thofe  fibres  have  receded  from  it,  it  is  continued 
{lender,  but  hollow,  for  fome  way  along  the  umbil- 
ical cord  ; in  which,  how'ever,  it  vaniflies.  Are 
not  the  other  parts,  though  not  yet  feen  in  the  hu- 
man fpecies,  fupported  by  the  very  ilrong  analogy 
of  brute  animals,  which  have  both  an  urachus  and 
an  allantois  ? But  a proper  receptacle,  continuous 
with  the  hollow  urachus,  fo  large  in  quadrupeds, 
has  not  yet  been  obferved  in  man  with  fufficient 
certainty,  or  not  fufliciently  often  ; and  thofe  emi- 
nent anatomifts,  who  have  obferved  a kind  of  fourth 
veffei,  continued  along  the  umbilical  cord  into  a 
proper  veficle,  do  not  confidcr  that  veflel  to  be  the 

urachus^ 


443 


CONCEPTION. 


Chap.  XXIX. 


urachus,  and  very  lately  have  referred  it  to  the  om- 
phalomefenteric  genus ; and  in  the  human  foetus, 
the  urine  is  feparated  in  a very  fmall  quantity  : nor 
perhaps  would  it  be  an  improbable  conjecture,  that 
lome  portion  of  the  urine  is  conveyed  from  the 
urachus  into  the  funiculus  umbilicalis,  and  its  fpon- 
gy  cellular  fabric,  and  there  effufed  ; and  therefore, 
that,  of  all  animals,  man  has  the  longeft  umbilical 
cord,  becaufe  he  alone  has  no  allantois.  It  is  cer- 
tainly fhort,  and  enters  into  the  cord,  but  does  not 
feem  to  reach  the  placenta.  Sometimes,  in  the 
adult,  it  has  remained  open,  and  has  contained 
urine  even  as  far  as  the  navel. 

Dcccc.  In  the  mean  time,  the  foetus  grows  ; the 
tubercles  of  the  limbs  gradually  fhoot  from  the 
trunk  ; and  the  further  moh  beautiful  evolution  of 
the  child  advances  to  perfection,  in  a manner  which 
cannot  be  defcribed  here,  and  not  yet  fufficiently 
by  anatomifts ; of  which,  however,  we  muft  premife 
a ilrort  account. 

Dcccci-  The  embryo  which  we  firft  faw  in  tl)C 
uterus  of  the  mother,  was  gelatinous,  having  fcarce- 
ly  a definite  form,  of  which  one  part  could  not  be 
cllftinguiflied  from  anotlicr.  There  was,  however, 
in  that  gluten,  a heart,  the  fource  of  life  and  mo- 
tion ; there  v/ere  veffels  which  generated  the  li- 
quor of  the  amnios  ; there  were  therefore  umbilical 
veffels,  and  the  trunks  of  the  yolk,  which  it  re- 
ceives from  the  foetus,  are  largeff  when  they  fir  if 
become  vilible.  There  was  both  a head  and  fpi- 
nal  column,  each  of  them  very  large,  and  larger  in 
proportion  than  at  any  other  time.  There  were 
likewife,  without  doubt,  the  reft  of  the  vifc^ra,  but 
in  a mucous  and  pellucid  ftate  ; for  which  reafon , 
they  may  be  obferved  fooner  than  is  to  be  expecbed 
naturally,  by  rendering  them  opaque. 

Dccccii.  But  in  every  part  of  the  foetus,  a very 
large  proportion  of  water  is  mixed  with  a very  lit- 
tle earth,  fo  that  the  verv  cellular  texture  is  in  an 

intermediate 


Chap.  XXIX, 


CONCEPTION. 


443 

intermediate  Hate  between  fluid  and  folid ; from 
large  drops  of  water  being  interpofed  between  dif,- 
tant  folid  elements. 

Dcccciii.  In  birds,  befldes  this  living  gluten, 
there  is  the  albumen,  which  is  of  a lymphatic  na- 
ture ; and  the  yoik,  which  is  oleaginous : in  man, 
there  is  a lafteous  fluid,  not  very  unlike  the  yolk, 
and  coagulable  lymph.  That  the  blood  is  prepared 
from  the  fat  by  the  proper  powers  of  the  foetus,  we 
are  perfaaded  from  the  example  of  birds.  From 
it,  are  gradually  prepared  the  other  humours,  and 
all  of  them  are  at  firft  mild,  void  of  take,  colour  and 
fmell,  and  of  a glutinous  nature*  The  peculiar  na- 
ture of  each  fupervenes,  at  a later  period,  in  fome 
of  them  not  till  many  years  after  birth,  for  inftance 
in  the  femen. 

Dcccciv.  The  elementary  folids,  even  in  the 
adult,  conftitute  much  the  fmalleft  portion  even  of 
the  harder  parts  of  the  human  body  ; in  the  foetus 
they  differ  from  the  fluids,  only  by  a fomewhat 
greater  degree  of  cohefion,  refembling,  as  yet  a 
gluten,  at  firft  fluid,  and  afterwards  of  greater  con- 
fiftence.  In  this,  the  fibres,  of  which  none  were  to 
be  diftinguiflied  in  the  primeval  embryo,  are  by  de- 
grees produced,  by  the  gluten,  as  it  feems,  being 
compreffed  between  the  neighbouring  veffels,  part 
of  the  water  exprelfed,  and  the  earthy  elements  at- 
tracling  each  other.  Thefe  fibres  varioufly  com- 
prehend one  another,  and  form  cellular  texture, 
even  morbidly,  and  intercept  little  fpaces,  in  which 
a fluid  is  contained.  Of  this  cellular  fubftance,  are 
formed  the  membranes  and  veffels,  and  almoft  the 
whole  body. 

Dccccv.  The  veffels  are  prior,  and  exift,  formed 
in  the  firft  appearance  of  the  embryo.  What  firft 
appears  diftinft,  and  formed  in  an  egg  during  in- 
cubation, are  venous  circles : but  thefe  veins  fuppofe 
arteries,  by  which  they  both  receive  their  fluid,  and 
the  motion  of  that  fluid.  They  are  not  generated 

mechanically, 


444 


CONCEPTION.  Chap.  XXIX. 


mechanically,  from  any  obftacle  to  the  courfe  of 
the  arterial  blood.  The  trunks  of  the  veins  are  firft 
vifible,  and  afterwards  the  branches  which  lead  to 
thefe  trunks.  If  they  were  produced  from  reflect- 
ed arteries,  the  branches  wmuld  firft  be  feen,  and 
the  trunks  formed  in  the  laft  place.  Nor  could  the 
arterial  blood,  if  repelled  by  an  obftacle,  form  thofe 
moft  beautiful  circles,  and  vefiels  ret.urning  into  the 
heart ; but  it  v/ould  rather  be  irregularly  diffufed 
through  the  cellular  texture.  And  the  primeval 
heart  would  foon  lofe  its  vitality,  unlefs  as  much 
fluid  returned  to  the  heart  by  the  veins,  as  was  fuf- 
ficient  to  maintain  its  pulfations. 

Dccccvi.  There  are,  therefore,  in  the  primeval  foe- 
tus, when  it  firft  becomes  vifible,  fome  things  more 
perfect  and  confpicuous  ; others  involved,  invifible, 
and  very  fmall.  The  heart  is  the  moft  perfect,  and 
the  only  moveable  and  irritable  part  ; although  it  is 
in  many  refpects  different  from  what  it  is  in  the 
adult.  The  brain  is  la^^e  and  fluid ; the  vefl'els 
formed,  which  appear  in  the  back,  next  to  the 
heart.  We  cannot  yet  diftinguifh  the  vifcera,  muf- 
des,  nerves,  limbs  ; the  bones  themfelves,  of  which 
the  firft  appearance  is  mucous,  or  the  veffels  of  the 
reft  of  the  body.  The  other  portion  is  the  abdo- 
men, of  which  the  umbilical  capfule  is  an  immenfe 
hernia. 

Dccccvii.  To  this  embryo  is  fuperadded  motion, 
in  man  almoft  of  the  heart  alone  ; and  aifo  in  birds, 
Vvdiofe  formation  does  not  take  place  without  a heat 
rather  greater  than  that  of  the  human  body  : yet, 
without  the  heart,  heat  deftroys,  inftead  of  forming 
the  foetus.  The  heart  is  proportionally  largeft  at 
the  very  firft,  and  afterwards  decreafcs  more  and 
more  in  comparifon  with  the  reft  of  the  body.  Its 
pulfations  are  alfo  at  this  time  very  frequent,  and 
in  the  very  foft  foetus  extremely  powerful,  in  impell- 
ing the  humours,  and  diftending  and  producing 
the  vefl'els. 


DCCCCVIII. 


Chap.  XXIX. 


CONCEPTION. 


445 

Dccccviir.  To  the  force  of  the  heart  is  oppofed, 
what  neverthelefs  is  of  fervice  in  the  formation  of 
the  foetus,  the  vifcidity  of  the  vital  humours  which 
unite  the  earthy  elements.  There  is  therefore  in 
the  embryo  both  an  impelling  force,  which  increafes 
the  longitudinal  growth  ; and  a reiifting  force, 
which  moderates  that  increafe,  and  increafes  the 
lateral  preffure,  and  thus  the  diftention.  By  the 
force  of  the  heart  all  the  arteries,  or  for  ealinels  of 
expreffion  the  artery,  which  reprefents  all  the  reft, 
with  ail  the  furrounding  cellular  texture,  is  length- 
ened out ; its  folds  are  fmoothed  out.  It  is  alfo  di- 
lated. And  the  blood  by  its  lateral  preffure  makes 
an  effort  againft  the  almoft  impervious  branches  of 
the  arteries,  fills  and  involves  them,  and  fets  them 
off  at  more  obtufe  angles  : thus  are  produced  fpaces, 
having  little  refiftance,  into  Which  the  gluten  is  de- 
pofited.  In  the  very  fubftance  of  the  artery,  while 
it  is  every  where  dilated,  between  its  imaginable 
folid  threads,  are  prepared  little  reticulated  fpaces 
like  the  interftices  of  a diftended  net,  which  are 
alfo  adapted  for  receiving  humours.  Thefe  are 
larger  round  the  heart  and  in  the  head,  whither 
the  impulfe  of  the  heart  is  more  direft,  and  in  the 
placenta  : they  are  fmaller  in  the  inferior  part  of 
the  body,  from  which  the  umbilical  arteries , fub- 
traft  the  greateft  part  of  the  blood. 

Dccccix.  The  foetus  increafes  very  quickly,  as 
is  moft  evident  in  the  example  of  the  chick  in  ovo, 
whofe  length  on  the  twenty  fecond  day  is  to  its 
length  the  firft  day  at  leaft  as  1,000,000  to  i ; and 
the  whole  increafe  of  bulk  in  the  bird  during  the 
remainder  of  its  life  does  not  exceed  the  fifth  part 
of  its  increafe  in  the  egg  during  the  firft  day.  For 
the  fcetus  has  a larger  and  more  irritable  heart, 
veffels  larger  in  proportion,  and  likewife  more  nu- 
merous and  relaxed,  and  its  folid  parts  are  mucous 
and  diftenfible.  The  breaft  is  later  formed,  and 

furrounded 


44S  CONCEPTION.  Chap.  XXIX. 

farrounded  with  membranes  fo  foft,  that  they  can- 
not be  feen^ 

Dccccx.  The  embryo  does  not  only  increafe  in 
bulk,  but  is  remarkably  altered  in  every  particular, 
fo  that  it  is  brought  forth  totally  di/hmilar  frcna 
what  it  was,  v/hen  it  firll  became  vifible.  And  lirft 
it  is  probable,  that  from  the  produclion  of  the  arte- 
ries of  the  limbs,  the  limbs  connected  to  tire  fides 
by  fome  gluten  are  feparately  evolved,  and  that  at 
firft  they  fprout  out  very  fhort,  but  afterwards  be- 
come gradually  longer,  and  divided  into  diltinct  ar- 
ticulations, as  the  wings  of  a butterfly  are  expand- 
ed by  the  extenflon  of  a network  of  veffels.  Thus 
likewife  the  right  ventricle  of  the  heart  is  expand- 
ed by  the  blood  coming  to  it  in  greater  quantity  ; 
and,  being  increafccl  by  degrees,  becomes  equal  to 
the  left. 

Dccccxi.  On  the  other  hand,  the  cellular  texture, 
from  its  glutinous  aqueous  nature,  becoming  grad- 
ually harder  by  the  addition  of  earthy  particles  ; 
by  a gentle  attraction  contracts  the  parts,  which 
were  before  ftraight,  into  various  flexures  ; and 
unites  the  auricles  to  the  heart,  from  which  they 
were  hitherto  feparate.  Thus  the  mufcles,  by  their 
action,  draw  out  tlie  proceffes  from  the  bones,  and 
dilate  the  fmail  cavities  into  large  cells  ; and  like- 
wife  incurvate  the  bones,  and  varioufly  modif)^  their 
fiiape. 

Dccccxii.  Preflure  has  much  influence  : to  it 
is  attributed  the  defeent  of  the  tefticles  into  the 
ferotum,  after  the  abdominal  mufcles  acquire  irrita- 
bility ; to  it  the  repuliion  of  the  heart  into  the 
breaft,  when  the  integuments  of  the  breaft  become 
larger  : to  it  alfo  the  lengthening  of  the  breaft,  the 
flrortening  of  the  abdomen,  and  the  leffeiung  of  its 
vifeera,  when  the  air  received  into  the  lungs  dilates 
the  cavity  of  the  thorax.  But  even  the  bones  arc 
varioufly  deprefied  by  the  preflure  of  the  mufcles, 
blood-vefl'els,  and  even  of  the  very  foft  brain  itfelf ; 


CONCEPTION. 


Chap.  XXIX. 


447 


and  by  the  fame  means  flelli  is  changed  into  ten« 
don. 

Dccccxiii.  The  power  of  derivation  brings  the 
blood  into  the  pelvis  and  lower  extremities,  from 
the  clofed  umbilical  arteries  : when  the  foramen 
Gvale  is  contra<Ted  by  the  auricles  drawn  towards 
the  heart,  it  evolves  the  right  ventricle  of  the  heart : 
when  the  veffels  of  the  yolk  have  occupied  the 
whole  length  of  the  egg,  and  can  receive  no  further 
elongation,  it  dilates  the  umbilical  arteries  of  the 
chick,  and  produces  a new  membrane  with  incred- 
ible celerity.  On  the  contrary,  but  by  the  fame 
power,  after  the  blood  has  acquired  a new  facility 
of  admifion  into  any  veffels,  the  other  parts,  to 
which  its  paffage  is  not  equally  eafy,  inereafe  lefs 
quickly.  The  growth  of  the  head  is  flower  after 
the  lower  limbs  have  begun  to  inereafe. 

Dccccxiv.  By  the  evaporation  of  the  thinner  part 
of  a fluid,  a membrane  may  be  formed,  as  in  the 
example  of  the  epidermis  ; or  cartilage,  as  hap- 
pens in  the  bones  : or  bone  itfelf,  or  fomething  of  a 
ftony  nature,  which  happens  very  frequently  in  the 
fliells  of  aquatic  animals.  The  bones  at  firft  are 
foft,  and  of  a mucous  nature ; then  they  acquire 
the  conflftence  of  jelly  j and  this  afterwards  be- 
comes a cartilage,  without  any  change  of  parts,  as 
far  as  can  be  obferved. 

Dccccxv.  Cartilage,  however,  is  not  fo  imper- 
ceptibly converted  into  bone.  It  never  happens, 
without  lines  and  furrows  having  previoufly  mark- 
ed the  cartilage  ; without  the  red  blood  making  a 
paffage  for  itfelf  into  the  veffels  of  the  bones  ; with- 
out thefe  veffels  manifeftly  penetrating  from  the 
nutritious  trunks  into  the  interior  of  the  bone,  and 
impinging  as  it  were  in  right  lines  on  the  cartilagi- 
nous extremity  of  the  body  of  the  bone,  which  they 
remove  farther  and  farther  from  its  middle.  Round 
thefe  veffels  are  formed  cellular  texture  and  lami- 
nse,  which  the  veffels  themleives  feem  to  comprefs 

into 


CONCEPTION. 


Chap.  XXIT. 


448 

into  a medullary  tube.  Laflly,  in  the  epiphylls, 
which  both  remains  cartilaginous,  and  denies  en- 
trance  to  the  blood  much  longer,  the  red  veffels  ]>en- 
etrate  through  the  extreme  cruft,  as  alfo  others 
which  come  from  the  exterior  veflels  of  the  limbs. 
Thus  alfo  in  the  epiphyfts  is  produced  a red  vafcu- 
lar  nucleus,  v/hich,  being  gradually  increafed  by 
veffels  fent  out  from  its  furface,  converts  the  reft  of 
the  cartilage  into  a bony  nature. 

Dccccxvi.  In  thefe  long  bones,  it  feems  evident, 
that  their  growth  is  owing  to  the  arteries  being 
elongated  by  the  force  of  the  heart,  and  gradually 
extended  to  the  extremities  of  the  bones : and  that 
the  hardnefs  is  owing  to  grofler  particles,  depofited 
in  the  cartilage,  after  its  veflels  have  admitted  the 
red  blood*  But  even  a bony  callus  never  becomes 
found,  till  newly  formed  red  veffels  have  penetrated 
its  fubftance. 

Dccccxvii.  The  flat  bones  originate  from  a kind 
of  membrane.  Over  this,  the  fibres  fpread  them- 
felves,  at  firft  in  a loofe  network,  and  afteiwards 
more  denfely,  having  a membrane  for  their  bafts ; 
the  pores  and  intervals  between  thefe  fibres  being 
gradually  contrafled  and  filled  wuth  a bony  juice, 
at  laft  convert  it  into  perfect  bone.  In  thefe  bones 
alfo,  ftraight  red  veffels,  are  diftributed  between  the 
fibres. 

Dccccxviii.-  The  phenomena  of  the  formation  of 
callus,  prove,  that,  between  the  primeval  fibres,  an. 
offeous  fluid,  replete  with  groffer  particles,  is  depof- 
ited, as  it  exudes  in  fmall  drops,  not  from  the  pe- 
riofteum,  but  from  the  inmoft  fubftance  of  the  bone, 
and  gradually  becomes  indurated.  But  even  che- 
mical analyfis  extraifts  that  gluten  from  the  bones  j 
and  in  anchylofis,  it  appears  poured  around  in  the 
manner  of  confiftent  fluid,  and  manifeftly  fills  up 
the  chinks  of  the  bones  and  intervals  of  the  futures. 
It  contains  grofs  earthy  particles,  which  have  been 
difeovered  bv  various  experiments  j and  the  juice 

of 


Chap.  XXIX.  CONCEPTION.-  449 

of  madder  adhering  to  it,  manifeftly  diftinguifhes 
it  by  its  colour. 

Dccccxix.  The  periofteum  covers  the  bones,  as 
membranes  the  vifcera ; and  from  it  cellular  pro- 
ductions follow  the  interior  veffels  of  the  bones  : 
but  the  periofteum  has  neither  ftraight  fibres,  nor 
the  habit  of  alveoli  or  laminoe,  nor  red  veffels,  while 
the  bone  in  the  egg  is  indurating ; nor  does  the 
periofteum  at  all  adhere  to  the  bone,  except  in  the 
epiphyfis,  when  its  bony  nature  is  fpreading  from 
the  middle  ; and  it  is  thinneft  when  the  bone  is  in 
a cartilaginous  ftate,  afterwards  it  becomes  every 
where  complete.  In  the  flat  bones,  it  every  where 
affords  a bafis  for  the  bony  fibres. 

Dccccxx.  Therefore  the  head  is  large,  every  where 
membranaceous,  and,  in  the  firft  days  of  geftation. 
Cartilaginous  in  few  places,  the  mouth  deep,  and 
the  jaws  long  ; alfo,  in  the  mature  foetus,  there  are 
the  rudiments  of  the  teeth,  to  which  a great  deal  of 
membrane  is  attached  ‘ the  brain  is  at  firft  fluid, 
and  always  foft ; it  is  alfo  large  ; and  the  nerves 
are  large  ; the  eyes  are  large,  and  the  pupil  is  Ihut 
by  a membrane  ; the  breaft  is  very  ftiort,  but  ex- 
panfile, on  account  of  the  great  quantity  of  cartil- 
age ; the  belly  is  large,  and  inclofed  with  mem- 
branes : the  liver  very  large  ; the  bile  is  inert  and 
mucous  : the  inteftines  are  flowly  irritable,  and, 
when  the  foetus  is  ripe,  are  full  of  green  foft  fasces  ; 
the  kidneys  are  divided  into  lobes,  and  large,  and 
renal  capfules  very  large  : the  pelvis  is  very  fmall, 
fo  that  the  ovaries,  the  bladder,  and  Fallopian  tubes 
project  above  it ; the  genital  fyftem  is  denfe,  not 
yet  evolved,  or  fecreting  its  fluids  : all  the  glands 
are  large,  efpecially  the  conglobate  glands,  and  full 
of  ferous  fluid  : the  fkin  is  at  firft  peUucid,  and  af- 
terwards covered  with  a foft  cuticle,  and  febaceous 
ointment  : the  fat  is  gelatinous,  and  afterwards 
grumous  ; and  the  tendons  foft,  fucculent,  and  not 
yet  fliining, 

F f DCCCCXXI. 


45^ 


CONCEPTION. 


Chap.  XXIX. 


Dccccxxi.  There  is  a great  difference  betM'ixt 
the  circulation  of  the  blood  in  the  foetus  and  in  the 
adult : that  this  may  be  underftood,  it  is  neceffary 
to  defcribe  the  organs  by  which  it  is  preformed. 
The  firft  is  the  th)unus,  a fort  loofe  gland,  confift- 
ing  of  many  lobes,  colleffed  into  two  larger  upper 
procellcs,  and  two  inferior  fhorter  ones,  which  are, 
however,  joined  together  by  a great  deal  of  long 
and  lax  cellular  texture  : this  gland  is  large  in  the 
foetus,  and  occupies  a great  part  of  the  breaft  ; it  is 
feated  in  the  cavity  of  the  mediaftinum,  and  in  part 
of  the  neck  ; and  is  wholly  filled,  in  its  very  inmofl 
ftruclurc,  with  a white  ferous  liquor,  which  cannot 
be  difeovered  without  wounding  it.  In  the  adult, 
being  comprefled  by  the  enlarged  lungs,  and  by 
the  aorta  now  become  larger,  it  gradually  difap- 
pears.  Of  the  ufe  of  this  gland  or  its  liquid,  we  are 
altogether  ignorant ; although  all  the  other  glands, 
efpecially  the  conglobate  ones,  are  alfo  larger  in  the 
foetus,  as  we  have  juft  now  obferved. 

Dccccxxii.  We  have  faid,  that  the  cavity  of  the 
breaft  is  flrort,  being  compreffed  by  the  enormous 
bulk  of  the  liver  j the  lungs  are  fmall  in  propor- 
tion to  the  heart,  and  folid  fo  as  to  ftnk  in  water, 
vdien  completely  excluded  from  the  air,  by  being 
furrounded  with  water.  Since,  therefore,  previous 
to  reipii'ation,  the  lungs  cannot  tranfmit  fo  great  a 
quantity  of  blood  as  they  do  in  the  adult  (ccxcii. 
ccxcYii,)  in  the  foetus  there  are  therefore  other  ways 
prepared,  by  v'hich  the  greateft  part  of  the  blood 
palfes  from  tlie  umbilical  vein  and  lower  cava,  into 
the  ?.orta,  without  entering  the  lungs.  In  the  pri- 
m.eval  foetus  there  is  no  right  ventricle  of  the  heart ; 
and  the  communication  between  the  right  auricle 
and  the  left  is  fo  large,  that  all  the  blood  which 
comes  by  the  vena  cava  paffes  immediately  into  the 
aorta,  a very  fmall  quantity  excepted,  which  goes 
to  the  very  fmall  and  invifible  lungs.  Afterwards, 
in  the  foetus,  now  grown  bigger,  the  lungs  are  in- 


Chap.  XXIX. 


CONCEPTION. 


451 

deed  larger,  and  the  paflTage  from  the  right  part  of 
the  auricle  into  the  left  is  narrower,  fmce  the  auri- 
cular canal  is  now  taken  entirely  within  the  heart, 
and  the  auricles  themfeNes  are  become  much  lliort- 
er.  But  yet  the  feptum,  which  is  common  to  the 
right  and  left  auricles,  is  perforated  with  a large 
foramen  ovale,  throus^h  which  the  blood  coming 
from  the  abdomen,  and  a little  repelled  by  the  val- 
vular margin  of  the  right  auricle,  (lxxxiii.)  flows 
in  a full  ftream  into  the  left  finus.  But  by  degrees 
the  membrane  of  each  finus  is  elevated  backwards, 
and  is  connefted  with  the  pulmonary  finus,  above 
the  oval  foramen,  by  an  upper  fibre  on  each  fide, 
and  then  by  many  lower  palmated  ones  in  fuccef- 
fion,  fo  as  to  clofe  up  at  firft  a fmall  part,  and  after- 
wards the  greater  part  of  this  foramen  ; fo  that  on- 
ly a tranfverfely  oval  oblique  paflage  is  left,  whicli 
remains  free  betwixt  the  round  margin  of  the  faid 
oval  foramen,  and  the  increafing  veflel  in  the  ma- 
ture foetus,  equal  to  about  a fifteenth  part  of  the 
mouth  of  the  vena  cava. 

Dccccxxiii.  That  the  blood  takes  this  courfe, 
and  that  no  part  of  it,  on  the  contrary,  flows  from 
the  left  finus  into  the  right,  is  confident  with  ^eve- 
ry fact.  For,  the  column  of  blood  in  the  right  finus 
is  very  large ; for  it  is  impofiible  there  fliould  be  a 
larger,  as  it  brings  back  the  blood  from  the  whole 
body ; and  the  left  auricle  contains  lefs  blood  than 
the  right,  as  part  of  it  flows  through  the  duclus  ar- 
teriofus,  whence  it  is  alfo  much  lefs  than  the  right : 
moreover,  the  valve  in  the  mature  foetus  is  fo  large, 
and  placed  fo  much  to  the  left  of  the  ifthmus  or 
mufcular  arch  (dccccxxii.)  that  when  impelled  from 
the  left  fide,  the  valve,  like  a Ihutter,  clofes  up  the 
foramen  ; but  being  impelled  from  the  right  fide, 
it  readily  gives  way,  and  tranfmits  either  blood  or 
flatus,  and  even  retains  flatus  itfelf,  when  blown 
from  the  right,  and  does  not  fuffer  it  to  return  to 
the  right  fide. 


F F 2 


DCCCCXXIV. 


CONCEPTION.  Chap.  XXIX. 


452 

Dccccxxiv.  Moreover,  but  a fmall  portion  of  that 
blood  which  entered  the  right  ventricle  paffes  to 
the  lungs ; for  the  pulmonary  artery,  being  in  the 
fcetus  much  larger  than  the  aorta,  is  continued  in 
a ftraight  line  into  the  duclus  arteriofus  ; which  is 
larger  than  the  joint  caliber  of  both  the  pulmonary 
branches,  and  greatly  larger  than  the  opening  of 
the  foramen  ovale,  and  which  enters  into  that  part 
of  the  aorta  which  firft  comes  in  conta^  with  tlie 
fpine,  under  its  fubclavian  branch  ; by  which  means 
it  transfers  more  than  half  the  blood  of  the  pulmo- 
nary artery  to  the  defcending  aorta,  which  mult 
otherwife  have  palTed  through  the  left  ventricle  in- 
to the  afcending  branches  of  the  aorta  ; and  this  is 
the  reafon  why  the  aorta  in  the  foetus  is  fo  fmall  at 
its  coming  out  from  the  heart.  By  this  mechan- 
ifm,  therefore,  the  lungs  are  relieved  from  preffurc, 
and  a great  part  of  the  blood  flows  in  a more  direft 
courfe  to  the  umbilical  arteries,  and  the  powers  of 
both  fidcs  of  the  heart  are  united  in  propelling  the 
blood  of  the  aorta. 

Dccccxxv.  Thofe  who  have  aflerted  that  the  foe- 
tus refpires  in  the  uterus,  having  made  ver\'  few 
obfervations,  have  neglected  that  moft  eafy  one 
which  is  derived  from  the  water,  in  tlie  middle  of 
which  the  foetus  fwims,  and  likewife  of  the  lungs, 
which  in  a foetus  are  conftantly  heavy,  and  fink  in 
water  ; and,  laftly,  the  evident  fliortnefs  of  the 
breaft,  and  fmallnefs  of  the  lungs.  Whether  it  can 
take  in  air  during  its  fhort  paflage  through  the  va- 
gina, is  more  diflicult  to  determine ; and  I fufpect, 
that  in  a certain  fituation,  a healthy  foetus,  not  too 
much  comprefled,  may  fometimes  infpire,  while  it 
is  in  part  ftill  impacted  between  the  parts  of  the 
mother. 

Dccccxxvi.  The  uterus  increafes  conftantly  along 
with  the  foetus  ; the  ferpentine  arteries  of  which  it 
is  compofed  being  extended,  and  rendered  ftraight, 
bv  the  blood  impelled  into  them  ; the  veins  being 

unable 


Chap.  XXIX. 


CONCEPTION. 


453 


unable  to  return  the  blood  into  their  trunks  com- 
preffed  by  the  great  bulk  of  the  uterus,  and  fweiling 
out  into  immenfe  finufes  ; and  laftly,  the  menftrual 
blood,  being  retained  in  the  uterus,  and  not  entire- 
ly fpent  on  the  ftill  fmaU  foetus.  Its  thicknefs  con- 
tinues the  fame,becaufe  the  greater  quantity  of  blood 
in  the  arteries  and  veins  coinpenfates  for  the  exten- 
uation of  its  folid  parts.  The  fundus  or  upper 
part,  efpecially,  increafes  ; fo  the  tubes  now  defcend 
from  the  middle  of  the  gravid  uterus.  The  ute- 
rus, therefore,  rifes  out  of  the  pelvis,  even  as  high 
as  the  colon  and  ftomach  itfelf,  and  compreffes 
the  abdominal  vifcera,  and  the  bladder  and  redum. 
The  os  uteri  in  the  firft  months  of  geftation  is  drawn 
upwards  along  with  the  uterus,  and  recedes  from 
the  entrance  of  the  vagina  : after  the  third  month, 
however,  it  again  defcends  and  immerges  into  the 
vagina.  The  fame  becoming  perpetually  Iliort- 
er,  projects  into  the  impervious  extremity  of  the 
vagina  : for  it  is  conftantly  becoming  more  ten- 
der ; and,  from  that  cartilaginous  hardnefs  which 
it  has  in  the  virgin  womb,  it  is  relaxed  into  a mu- 
cous foftnefs.  Never  perfectly  clofed  together,  it  is 
covered  and  defended  from  the  air  by  the  mucus  of 
the  f nufes,  and  perhaps  by  that  of  the  veiicles  which 
are  feated  in  the  cervix  uteri.  Finally,  the  cervix, 
which  remains  long  unchanged,  at  length,  during 
the  laft  months  of  geftation,  becomes  likewife  fhort, 
and  its  opening  becomes  flat  and  broad,  without 
length  ; and  towards  the  time  of  delivery,  is  always, 
more  open.  At  the  fame  time,  the  foetus  increafing, 
which  in  the  firft  months  had  no  certain  fituation, 
and  about  the  middle  of  the  time  of  geftation,  was 
often  rolled  together  into  a globe,  fo  that  the  head 
lay  betwixt  the  knees,  finks  its  ponderous  head  more 
and  more  into  the  pelvis,  and  direds  it  towards  the 
cervix  uteri.  , — 

Dccccxxvii.  The  various  complaints  in  the  ute- 
rus are  now  increafed  to  the  higheft  degree.  Being 

diftended 


454 


CONCEPTION. 


Chap.  XXIX. 


diftended  by  the  blood  retained  in  it,  all  its  nerves 
are  irritated  ; for  nothing  is  more  difagreeable  to 
man,  than  exceffive  tenfion,  unlefs  it  occurs  very 
gradually.  From  the  head  of  the  foetus,  funk  into 
the  pelvis,  the  rectum,  bladder,  and  that  part  of  the 
uterus  next  to  the  neck,  and  the  moft  fenfible,  are 
prelfed,  and  become  painful ; the  foetus,  having  ac- 
cjuired  its  full  bulk,  diftends  the  uterus  everyway  ; 
and  with  greater  uneafmefs,  becaufe,  the  waters  be- 
ing now  taken  away,  the  projecting  limbs,  and  the 
head,  prefs  much  more  Itrongly  on  the  uterus.  It 
is  alfo  thought,  that  the  placenta  itfelf,  now  very 
large,  diftends  the  naked  internal  furface  of  the  ute- 
rus. From  thefe  caufes,  arife  at  firft  tranfient  ef- 
forts of  the  irritated  uterus,  to  free  itfelf ; and  at 
laft,  vehen  thefe  caufes  have  got  to  their  utmoft 
height,  an  uneafy  fenfation  is  occaftoned  by  the  im- 
pacfed  head  of  the  foetus,  like  that  which  arifes  from 
a collection  of  faeces  in  the  reclum  ; by  \^'hich  pain, 
therefore,  the  mother  is  forced  to  attempt  the  birth 
of  the  child.  The  time  of  delivery  arrives  at  the 
expiration  of  nine  folar  months,  and  is  in  the  fame 
manner  defined  in  every  fpecies  of  animals,  although 
by  particular  caufes  it  may  be  accelerated  or  retard- 
ed for  fome  v^eeks,  provided  thefe  caufes  be  afeer- 
tained,  and  their  power  not  extended  too  far. 

nccccxxvin.  'formented  by  tenefmus,  now  be- 
come intolerable,  the  mother  exerts  the  whole  ef- 
fort of  a veiy  deep  infpiration,  by  which  the  vif- 
cera  of  the  abdomen  being  forced  downwards,  prefs 
upon  the  uterus,  (dcclvi.)  while,  at  the  fame  time, 
the  v'omb  itfelf,  being  contraded  by  its  contractile 
force,  urges  the  foetus,  fo  as  fometimes  to  exclude  it, 
vithout  any  efforts  of  the  mother.  The  difficulties 
of  the  birth,  however,  are  evidently  overcome  prin- 
cipally by  the  efforts  of  the  mother,  when  the  mouth 
of  the  uterus,  now  very  foft,  fuffer«  itfelf  to  be  dif- 
tended by  the  head  of  the  foetus.  For  the  amnios, 
filled  with  water,  protruded  in  the  form  of  a cone, 


Chap.  XXIX. 


CONCEPTION. 


455 

by  the  head  of  the  foetus,  dilates  the  os  internum 
uteri, becomes  extenuated,  and  diftended,and  burlts ; 
the  waters  efcape,  which  lubricate  the  paffage  of  the 
■vagina,  and  relax , all  the  parts.  Then  the  naked 
head  of  the  foetus,  with  the  face  turned  towards 
the  os  facrum  on  account  of  its  weight,  and  being 
urged  forwards,  like  a wedge,  dilates  the  os  uteri ; 
till,  by  a very  powerful  effort  of  the  mother,  the 
bones  of  the  pubes  being  often  fomewhat  loofened 
with  intolerable  pain  to  the  mother,  and  tremor  of 
the  whole  body,  the  head  is  preffed  out,  and  advan- 
ces through  the  dilatable  vagina,  which  is  not  very 
much  comprelfed  by  any  bone  ; and  the  foetus  is 
brought  forth,  with  difficulty  even  in  quadrupeds, 
but  moft  difficultly  in  the  human  race,  whofe  foetus 
has  the  largeft  head. 

Dccccxxix.  It  is  natural  for  women  to  have  but 
one  child  at  a birth,  which  law  they  have  in  com- 
mon with  all  the  larger  animals,  except  the  carniv- 
orous. Frequently,  however,  they  have  two,  more 
rarely  three,  and  never  more  than  five.  It  is  not 
to  be  doubted,  that  a fecond  foetus  may  be  conceiv- 
ed, while  the  firft  remains  in  the  uterus  : fince  wo- 
men have  frequently  iDorn  children,  in  whofe  ute- 
rus a hard  and  offified  foetus  had  been  long  re- 
tained. 

Dccccxxx.  The  placenta,  connefted  with  the 
fundus  uteri,  (dccclxxxviii.)  is  generally  fepara- 
ted  without  difficulty  in  a mature  birth,  by  weaker 
throes  of  the  mother,  and  by  the  art  of  the  mid- 
wife. Thus  the  fiocculi  of  the  placenta  are  drawn 
out  from  the  villi  of  the  womb,  a confiderable  flow 
of  blood  takes  place,  and  the  mother  is  delivered 
of  the  fecundines.  At  the  fame  time,  the  umbil- 
ical cord  is  tied  ; for  it  cannot  be  left  open  in  a 
healthy  and  lively  child  without  danger  ; and  is  cut. 
^riius  the  umbilical  vein  is  deprived  of  its  fupply  of 
blood,  and  an  infuperable  obftacle  is  oppofed  to  the 
arteries  of  the  fame  name. 


DCCCCXXXI. 


45^ 


CONCEPTION. 


Chap.  XXIX, 


Dccccxxxi.  The  uterus,  which  hitherto  had 
been  exceffively  diftended,  now  contracts  itfelf  by 
the  power  of  its  elaftic  fibres,  (dcccxliii.)  fo  fud- 
denly  and  powerfully,  as  often  to  catch  the  hand 
of  the  deliverer,  and  the  placenta,  if  it  be  not  foon 
loofened.  Thus,  the  veffels  are  compreffed,  alfb  con- 
tracting to  a lefs  fize  by  their  own  pov^er  ; whence 
the  large  quantity  of  blood  that  was  collected  in 
the  uterus,  is  expreffed  and  flows  out  under  the  de-r 
nomination  of  the  lochia  ; at  firft  pure  blood,  but 
afterwards,  as  the  veffels  contract  themfelves  more 
clofely,  it  becomes  yellow,  and  afterwards  white  ; 
and  the  extenfive  wound  of  the  uterus  is  healed, 
which  foon  fhrinks  to  a bulk  not  much  exceeding 
that  of  the  viroin  uterus. 

O 

DccccxLiv.  But  two  or  three  days  after  delivery, 
when  the  firft  violence  of  the  lochial  difchara;e  lias 
abated,  the  breafts  fwell  confiderably  ; and  as  in 
the  time  of  geftation  they  yielded  a little  ferum, 
they  now  become  turgid,  at  iirft  with  a ferous,  thin 
fluid,  which  is  foon  followed  by  tlie  chyle  itfelf. 
For  milk  very  much  refembles  chyle,  but  human 
milk  lefs  than  that  of  other  aniinals.  It  is  white, 
thickifh,  fweet,  and  replete  with  a very  fweet  ef- 
fential  fflt,  grorvs  four  fpontaneoufly,  but  is  tem- 
pered by  the  addition  of  oil  and  lymph,  and  is  com- 
pofed  of  an  odorous  volatile  halitus,  a good  deal  of 
fat,  water,  vifeid  cheefy  matter,  and  an  earthy  fub- 
ftance  rather  alkalefcent ; by  fafting  fame  time,  from 
the  chyle  being  then  converted  into  ferum,  the  milk 
becomes  fait,  alkalefcent,  and  difpleafmg  to  the  in- 
fant. Like  the  chyle,  it  frequently  retains  the  nature 
of  feme  kinds  of  aliments  and  medicines.  The  caufe 
of  this  increafed  fecretion  in  the  breafts,  feems  to  de- 
pend on  revulfion,  and  to  fucceed  the  fupprefllon 
of  that  plentiful  uterine  fecretion  by  which  the 
feetus  was  nouriflied  ; as  diarrhoea  fucceeds  fuppref- 
fed  perfpiration.  For  it  has  been  obferved,  that 
true  milk  has  been  difeharged  from  other  parts. 


Chap^  XXIX. 


CONCEPTION. 


45? 

;ind  even  through  wounds.  And  there  is  belides 
between  the  uterus  and  breafts,  fome  kind  of  ner- 
vous fympathy,  and  a fimilar  fitnefs  for  generating 
a white  liquor.  For  the  uterus  in  infancy,  and  dur- 
ing pregnancy,  manifeftly  generates  it.  But  the 
inofculations  betwixt  the  mammary  and  epigaftric 
arteries,  though  true,  are  fo  fmall,  that  in  this 
nothing  is  to  be  afcribed  to  them, 

DccccxLv.  The  breafts  are  compofed  of  a very 
large  quantity  of  very  foft  and  very  white  fur- 
rounding fat and  of  a conglomerate  convex  gland, 
confifting  of  round,  hard  kernels,  of  a reddifli  blue 
colour,  furrounded  externally,  and  connected  to- 
gether, by  firm  cellular  fubftance,  feparating  into 
fmaller  acini ; which  ftrucfure  is  common  to  men 
and  women.  To  thefe  glands  many  veffels  are 
diftributed  from  the  internal  mammaries,  from  the 
external  thoracics,  and  laftly  from  the  humeral  ar- 
tery, all  which  mutually  inofculate  near  the  nipple. 
The  trunks  of  the  mammary  arteries,  but  not  the 
mammales,  inofculate  with  the  epigaftric  velfels ; 
the  veins  more  evidently.  The  nerves,  both  large 
and  numerous,  as  in  cutaneous  parts,  are  derived 
from  the  nerves  placed  between  the  upper  ribs. 

DCcccxLvi.  From  the  middle  of  this  gland  of 
the  breaft,  and  likewife  from  the  furrounding  fat, 
from  an  infinite  number  of  roots,  numerous,  very 
flender,  foft,  white,  and  dilatable  dufts  arife,  which 
converge  on  all  fides  to  the  nipple  in  the  centre,  both 
into  the  circle  which  lubtends  its  bafe,  and  into  the 
area  of  that  circle,  and  emerge  into  the  root  of  the 
nipple.  This  is  a cavernous  cellular  body,  into 
which  the  blood  may  be  effuied,  fo  as  to  caufc 
ereclion,  as  in  the  penis.  This  papilla  is  perfora- 
ted by  twenty  or  more  excretory  duels  from  the 
breaft,  called  la<ftiferous ; between  which  there  is 
not  any  inofculation,  and  which  are  much  narrow- 
er in  the  nipple,  than  before : and  in  the  flaccid 
ftate  of  the  nipple,  are  compreiied,  wrinkled,  coL 

lapfed. 


45S  CONCEPTION.  Chap.  XXIX, 

lapfed,  and  fliut ; but  when  the  nipple  is  erected 
by  any  kind  of  titihation,  they  become  ftraight  and 
have  patulent  mouths,  lying  betwixt  the  cutaneous 
wrinkles.  This  papilla  is  furrounded  by  a circle 
furnilhed  with  febaceous  glands,  which  defend  the 
tender  fkin  againft  attrition  and  perpetual  moif- 
ture. 

DCcccxLVii.  This  is  the  firft  food  of  the  infant, 
and  at  other  times  alfo  is  exceedingly  falutary  to 
man.  This  the  infant  knows  how'  to  take,  before 
it  has  attempted  to  perform  any  other  function  of 
the  body.  Taking  the  nipple  in  its  mouth,  it 
carufes  it  to  fiveU  by  gentle  vellications,  and  prelTes 
it  wdth  the  lips,  that  no  air  may  enter  betw'ixt 
them ; at  the  fame  time,  it  infpires  and  forms  a 
fpace  in  its  mouth,  in  w'hich  the  air  is  rarelied  ; 
and  thus,  the  preffure  of  the  air,  and  the  compref- 
fing  force  of  the  lips  of  the  infant,  emulges  the 
milk  from  the  nipple,  from  which,  on  account  of 
its  quantity,  it  is  moreover  difpofed  to  flow  fpon- 
taneoufly  ; and  the  infant  fucks,  and  is  nourilhed. 
The  firft  ferous  milk,  termed  coloftra,  loofens  the 
bow^els  of  the  young  infant,  and  evacuates  the  me- 
conium, (dcccxcviii.)  to  the  great  advantage  of 
the  child.  Yet,  even  independent  of  the  foetus. 
Ample  titillation  erecting  the  nipples,  and  increaf- 
ing  the  afflux  of  blood,  has  produced  a flow  of 
milk,  even  from  virgins,  old  women,  and  men. 
Milk  is  only  generated  after  puberty  ; befewe  that 
time  a ferous  humour  flows  from  the  breaft  ; and 
for  the  moft  part  it  is  nrft  generated  about  the  mid- 
dle of  pregnancy.  After  the  menfes  have  ceafed, 
the  breads,  as  well  as  the  uterus,  being  grown 
effete,  ceafe  to  perform  their  office. 

DccccxLviii.  But  great  changes  happen  to  the  ir^ 
fant  when  born.  The  Arft  is  refpiration,  which  it 
attempts  even  wdthin  the  vagina  of  the  mother  ; be- 
ing probably  excited,  by  various  pain  and  anxiety, 
to  thofe  cries  with  which  it  falutes  the  light,  and 

perhaps 


Chap.  XXIX.  CONCEPTION. 


459 

perliaps  by  the  delire  of  food  which  Is  obtained  from 
the  {lore  of  the  amnios  : therefore,  it  draws  air  into 
its  lungs,  and  dilates  them,  till  now,  fmall  and  full 
of  ferous  humours,  and  changes  them  from  being  of 
a deep  red  colour,  fmall,  folid,  and  linking  even  in 
fait  water,  into  a fubftance,  which  is  light,  fpongy 
and  floating,  large,  full  of  air,  and  almoil  of  a 
white  colour  : therefore,  the  blood  enters  more  ea- 
fily  into  thefe  enlarged  and  loofe  lungs,  (cclxv.) 
in  confequence  of  which,  a large  portion  of  the 
blood  of  the  pulmonary  artery,  that  went  through 
the  canalis  arteriofus  into  the  aorta,  no\v  pall’es  into 
the  lungs  by  the  other  branches  of  that  artery. 
And  the  duel  is  hill  more  deferted,  as  there  is  a 
new  obhacle  to  the  defeent  of  the  blood  into  the 
abdomen  ; for  the  very  large  umbilical  arteries  are 
now  tied,  fo  that  the  blood  of  the  defeending  aorta 
cannot  now  find  its  way,  but  by  an  effort  with  which 
it  dilates  all  the  arteries  of  the  pelvis  and  lower  ex- 
tremities. Finally,  as  the  lungs  receive  more  blood, 
the  aorta  arifing  from  the  heart  alfo  receives  a great- 
er quantity,  and  the  intermediate  duflus  arteriofus 
is  comprefl'ed  between  the  tumid  aorta  and  the  pul- 
monary artery,  fo  that  in  the  adult  it  is  found  not 
only  empty  but  flaortened  ; in  other  refpecls  it  is 
• fingularly  red  within,  foft,  and  very  apt  to  concrete 
with  hagnating  blood.  This  courfe  of  the  blood, 
therefore,  is  foon  aboliflied,  commonly  within  a 
year. 

DccccxLix.  Then  the  foramen  ovale  is,  by  the 
fame  caufes,  alfo  gradually  clofed  up.  For  as  foon 
as  the  paffage  into  the  lungs  is  rendered  eafier,  the 
palfage  into  the  right  fide  of  the  heart  alfo  becomes 
eafier  ; whence  the  blood  of  both  cavas  flows 
thither  more  plentifully,  as  it  is  invited  by  the  lax 
pulmonary  artery,  and  therefore  does  not  need  that 
paffage  excavated  in  the  feptum  of  finufes.  Again, 
the  umbilical  vein,  being  now  almoft  deilitute  of 
any  fupply  of  blood,  on  account  of  the  umbilicus 

being 


CONCEPTION.  Chap.  XXIX. 


460 

being  tied,  (dccccxxx.)  lefs  blood  will  flow  into 
tlielower  cava,  and  confequently  the  preflure  againit 
tlie  foramen  ovale  will  be  diminilhed ; into  which, 
moreover,  the  blood  of  the  upper  cava,  on  account 
of  the  ifthmus,  will  be  fcarcely  able  to  penetrate. 
Laftly,  as  more  blood  is  conveyed  through  the 
lungs  into  the  left  fmus,  it  is  dilated,  and,  along 
with  the  whole  flnus,  the  cornicles  of  the  oval  valve, 
which  are  fixed  to  it,  are  extended,  and  elevate  tlie 
valve  ; fo  that,  in  the  mature  foetus,  being  drawn 
over  the  ifthmus,  it  entirely  fhuts  up  the  paflage, 
and  is  clofely  applied  to  the  ifthmus,  while,  at  the 
fame  time,  the  blood,  within  the  left  flnus,  fupports 
the  valve  againft  the  impulfe  of  the  blood  within 
the  right  flnus.  Thus,  by  the  acceflion  of  a little 
friclion  of  the  uppermoft  margin  of  the  valve  againft 
the  fuperior  ifthmus,  the  foramen  ovale  clofes  up 
by  degrees,  and  the  upper  margin  of  the  valve  is 
agglutinated  and  coheres  to  the  pofterior  furface  of 
the  ifthmus.  But  this  takes  place  very  flowly  ; fo 
that,  very  frequently,  even  at  an  advanced  age,  a 
fmall  aperture  ftill  remains  between  the  ifthmus 
and  upper  part  of  the  valve ; and  where  there  is  no 
aperture,  yet  there  are  the  remains  of  the  whole 
foramen,  hollow  to  the  left  flde,  and  of  a paflage  at 
the  upper  part,  open  towards  the  right  flde,  and 
clofed  to  the  left,  becaufe  the  power  of  the  blood 
in  the  right  fide  is  always  either  greater  than  its 
reflftance  on  the  left,  or  certainly  not  lefs,  even  in 
the  advance  of  life. 

Dcccci^  The  umbilical  vein,  being  deprived  of 
blood,  foon  clofes  up.  I'he  blood  of  the  vena  porta- 
rum,  being  no  longer  impeded  by  an  oppoflte  force 
.coming  from  the  umbilicus,  occupies  the  left  flnus 
and  curve  of  the  umbilical  fofla,  (ncxcv.)  and 
tranfmits  blood  through  thofe  branches  by  wliich 
the  umbilical  vein  formerly  fer  t blood  into  the  cas  a. 
The  duefus  venofus  being  neglected,  clofes  by  tlic 
new  compreflion  which  the  diaphragm,  defce;idi;ig 


Chap.  XXIX,  CONCEPTION.  4^4 

in  infpiration,  makes  againft  -the  liver ; by  v/hicli 
the  left  lobe  -of  the  liver  is  preffed  towards  the  lo*- 
buk,  and,  perhaps  too  from  the  obtnfe  angle  which 
it  makes  with  the  left  finus  of  the  vena  portarum  5 
for  it  is  certainly  firfl:  clofed  next  the  vena  porta- 
rum. 

DccccLi.  The  umbilical  arteries  are  clofed  up  in 
the  fame  way  as  other  arteries  ufually  are  when 
tied,  by  part  of  the  blood  being  coagulated  into  a 
polypus,  which  fills  up  the  impervious  extremity, 
and  by  the  blood,  which  meets  with  refilling  mem- 
branes, diverging  into  the  adjacent  lefs  reflfting 
branches.  Nor  do  I overlook  the  force  of  the  ab- 
dominal mufcles,  by  which  thofe  arteries  are  com- 
preffed  againft  the  full  abdomen  in  refpiration  5 or 
the  very  acute  angle  in  which  the  umbilicalis,  arif- 
ing  from  the  iliac  artery,  and  now  incurvated  with 
it  along  the  bladder,  makes  ; or  the  ftraight  direc- 
tion in  which  the  thighs,  which  in  the  foetus- made 
an  acute  fold  with  the  body,  are  now  extended. 
Thus,  thefe  arteries  are  foon  fhut  up,  leaving  only 
a very  fmall  tube,  that  leads  to  two  or  three  arteries 
of  the  bladder.  The  urachus  is  very  quickly  oblit- 
erated, from  its  afcending  directly  from  the  bladder, 
being  a very  flender  tube,  having  no  outlet,  and 
now  negle&ed  on  account  of  the  defcent  and  per- 
me-ability  of  the  urethra. 

DccccLii.  From  limilar  caufes  the  liver  is  grad- 
ually diminifhed,  and  contrafts  itfelf  within  the 
ribs  ; and  the  inteftina  crafla,  from  their  flender 
condition  in  the  foetus,  dilate  to  a confiderable  di- 
ameter, and  the  ftomach  is  elongated  j and  the  cx- 
cum  is  formed  by  the  weight  of  the  faeces  prefling 
downwards  on  the  right  of  the  appendix  ; and  the' 
lower  extremities  are  remarkably  enlarged  by  the 
repulfion  of  the  blood,  from  the  umbilical  arteries 
now  tied ; and  the  other  changes  take  place,  by 
which  the  foetus  infenfibly  advances  to  the  nature 
of  a perfed  adult. 


CHAP. 


NUTRITION. 


Chap.  XX^!. 


462 


CHAP.  XXX. 

NUTRITION,  GROWTH,  LIFE,  AND  DEATH. 

DCCCCLIH.  |P  VEN  after  ths  child  is  borrij  it  con- 
j tinues  to  grow,  but  always  more 
Ilowly  in  proportion  to  its  age.  There  are  many 
caufes  for  the  perpetual  diminution  of  its  grow'thi 
Many  veffels  feem  to  be  obliterated,  both  becaufe 
they  are  comprefTed  by  the  neighbouring  torrent 
of  fome  large  artery,  and  becaufe  the  blood,  now  be- 
come more  vifeid,  coagulates.  Befides,  the  food 
being  now  coarfer,  accumulates  in  the  blood  more 
earth,  which,  being  carried  through  the  whole  body 
with  the  nutritious  fluid,  renders  every  part  of  it 
harder,  bones,  teeth,  cartilages,  tendons,  ligaments, 
veffels,  mufcles,  membranes,  and  cellular  fubftance  ; 
lb  that  an  Increafe  of  hardnefs  may  be  perceived, 
even  by  the  touch.  Wherefore,  fince  the  blood 
flows  from  the  heart  through  fewer  canals,  and 
fince  all  the  parts  which  flaould  be  lengthened  or 
diftended  have  become  harder,  it  necdlarily  follows, 
that  thofe  which  ought  to  increafe  in  bulk,  will 
yield  lefs  and  lefs  to  the  impulfe  of  the  , heart. 

DCCccLiv.  But  the  heart  likewife,  which  is  the 
part  that  is  lirlt  cOnfolidated  of  all  the  foft  ones, 
increafes  lefs  than  any  other  part  of  the  whole  body; 
and  while  the  mucli  more  tender  limbs  and  Ibfter 
vifeera  are  diftended,  the  heart  itfelf  grows  more 
flowly,  and  continually  bears  a lefs,  and  at  laft  an 
eight  times  fmaller,  proportion  to  the  reft  of  the 
body  in  the  adult.  At  the  fame  time,  from  that 
very  denftty  which  it  has  fo  quickly  acquired,  it 
becomes  lefs  irritable,  and  is  contracled  lei's  fre- 
quently within  a given  time.  I'hus,  while  tlie  re- 
fifting  powers  are  augmented,  the  diftending  ones 
are  at  the  fame  time  diminiflied. 


DCCCCLV. 


Chap.  XXXi 


GROWm 


4^3 

DccccLv.  There  will,  therefore,  fooner  or  later, 
be  an  end  of  increafe  ; and  this  will  happen  fooner, 
in  proportion  to  the  quicknefs  and  frequency  of  the 
contra<d:ions  of  the  heart,  and  will  approach  when 
the  cartilaginous  crufts  of  all  the  bones  are  now  be- 
come fo  thin  that  they  cannot  yield  or  give  way  to 
the  increafe  of  the  bony  part.  In  women,  the  men- 
fes  feem  to  put  an  earlier  ftop  to  the  growth-  In 
cartilaginous  fifties  the  growth  is  perpetual. 

DccccLvi.  There  is  no  durable  ftate  j for,  nature 
from  the  firft  conception,  tends,  by  a perpetual  pro- 
grefs,  towards  decreafe.  It  is  faid,  however,  to  take 
place,  when  there  is  neither  any  increafe  of  bulk, 
nor  yet  any  very  vifible  decreafe. 

DccccLvii.  For  we  are  all  perpetually  confumlng 
(ccccxxxiv.)  Nor  do  v/e  only  lofe  the  fluid  parts 
of  our  bodies,  but  even  thofe  which  are  reckoned 
the  moft  folid.  For  even  the  bones  are  changed  ; 
and  the  teeth,  which  are  harder  than  the  bones, 
increafe  in  bulk  when  the  attrition  of  the  oppofite 
teeth  ceafes  to  wear  them  away,  and,  therefore, 
their  elements  are  changed  : even  the  fibres  of 
ivory  in  the  elephant’s  tooth  have  given  way,  and 
furrounded  on  each  fide,  in  curved  lines,  a leaden 
ftiot ; the  bony  juice  likewife  is  changed  ; fince  in 
fome  cafes  the  bones  grow  foft ; in  others,  it  forms 
bony  tumors : even  cicatrices  themfelves  have  a 
manifeft  growth,  for  otherwiie  they  would  not  be 
fufficient,  in  an  adult,  to  fill  up  a wound  received 
in  infancy  ; and  a great  quantity  of  the  earthy,  cer- 
tainly of  the  animal  part  of  our  bodies,  goes  off"  by 
urine,  as  is  proved  by  fome  difeafes. 

DCcccLviii.  The  caufes  of  the  deftruflion  of  the 
folids  confift  in  the  perpetual  extenfion  and  retrac- 
tion, which  happens  at  every  pulfation  of  the  heart, 
of  which  there  are  an  hundred  thoufand  every  day, 
a degree  of  motion  by  which  metals  themfelves  are 
worn  ; then  in  the  friftion  of  the  fluids  againft  the 
folids  3 the  wearing  away  of  all  the  membranes, 

which 


GROWTH. 


Chap.  XXX. 


4C4 

which  termlmate  with  a loofe  extremity,  either  on 
the  furface  or  in  the  internal  cavities  of  the  body, 
■i^  hich  are  fupported  folely  by  the  reft  of  the  canal ; 
in  the  alternate  fwelling  and  collapfe  of  the  mufcles ; 
and  in  the  attraction  and  preffure  which  our  mufcles 
exert.  But  the  parts  of  our  body  are  the  fooner 
worn  away,  that  they  conftft  of  a great  deal  of 
gluten  combined  with  a fmall  quantity  of  earth  ; 
and  that  gluten,  when  it  is  extended,  if  the  exten- 
fion  has  been  a little  fuperior  to  the  force  of  co- 
hehon,  muft  of  neceffity  fall  away  and  be  carried 
off  from  the  earthy  parts.  Thus,  deficiencies  are 
generated,  fuch  as  are  vilible  in  the  arteries  of  old 
men.  The  cellular  texture,  which  otherwife  would 
be  difft)lved  in  water,  into  a jelly,  is  worn  away  by 
the  friftion  produced  by  the  impetus  of  the  blood 
preffing  againft  the  neighbouring  blood-vclVels  and 
mufcles,  and  by  the  perpetual  alternation  of  flexion 
and  extenflon. 

DccccLix.  This  decreafe  would  be  very  quick 
and  indeed  there  would  be  no  great  diftance  be- 
tween the  end  of  our  hfe  and  its  besinnins;,  unlefs 
thefe  Ioffes  were  repaired.  The  fluid  parts  are  re- 
ftored  by  the  aliments,  and  that  pretty  quickly  ; as 
appears  from  the  example  of  a chicken,  in  which 
blood  is  generated  from  its  aliment  within  two  days. 
The  fat,  however,  and  red  globules  of  the  blood, 
are  formed  out  of  the  fat,  as  is  fhov.m  elfewhere  ; 
the  lymphatic  juice  from  the  jelly  ; the  mucus, 
from  mucus  5 and  the  reft  of  the  humours,  Irom 
thefe  and  water.  The  lolids  are  repaired  aimoil 
by  the  fame  means  which  we  have  deferibed  in 
the  hiftory  of  the  foetus.  A gelatinous  juice  is  con- 
veyed from  the  aliments,  through  the  arteries,  to 
all  parts  of  the  body,  and  exudes  into  the  cellular 
texture  every  where.  The  furrows,  vchich  we  im- 
agine to  be  made  in  the  inmoft  arterial  membrane 
by  the  impetus  of  the  blcoi,  are  filled  up  by  a 
vifeid  matter,  applied  to  them  by  the  lateral  prd- 

lurc; 


Chap.  XXX.  GROWTH.  465 

fure  ; never  in  too  great  quantity,  becaufe  the 
exuberant  parts  of  the  nutritious  particles  muft  ne- 
ceffarily  be  abraded  by  the  current  of  the  blood. 
Nor  will  it  be  deficient  while  there  is  a fufficient 
quantity  of  aliment,  fince  there  is  more  reft,  and 
lefs  refiftance  in  the  bottom  of  the  furrow,  which  is 
farther  removed  from  the  motion  of  the  blood 
through  the  centre  of  the  veffel.  There  feem  to 
be  certain  powers  in  the  ain,  by  which  the  aliment 
is  attached  to  the  folid  patts,  although  we  are  ig- 
norant of  the  manner  in  which  they  aft:. 

DccccLx.  The  decreafe  of  the  cellular  texture 
arifing  from  attraftidn  or  preffure  is  repaired  by 
the  vifcid  vapour  exhaling  from  the  artery,  and  ap- 
plied  to  the  wafted  places  by  the  force  of  the  neigh- 
bouring arteries  and  comprefling  mufcles,  its  aque- 
ous part  being  exprefled  and  abforbed.  The  glu- 
ten repairs  moft  of  the  organic  parts,  tendons,  and 
membranes  ; being  formed  into  new  cellular  fub- 
ftance,  as  in  the  foetus. 

DccccLxi;  The  wafte,  which  takes  place  in  the 
linconnefted  extremities  of  parts  adhering  by  their 
Other  extremity  to  the  reft  of  the  body,  can  be  re- 
paired by  protrufion  alone,  while  the  lymph  fills  up 
the  intervals  produced. 

DccccLXii.  When  the  growth  of  the  body  can 
proceed  no  further,  fatnefs  fupervenes,  which  is  a 
kind  of  imitation  of  real  growth.  This  proceeds 
from  the  fat  generated  by  the  aliment  ; which, 
from  the  impetus  of*t^e  blood  being  now  leflened 
as  it  enters  the  fmall  vefiels  with  more  difficulty,  is 
removed  to  the  fides  of  the  vefiels  ; enters  the 
lateral  vefiels,  and  inorganic  pores  of  the  arteries  ; 
exudes  into  the  cellular  texture ; and  there  is  ac- 
cumulated, in  confequence  of  the  diminution  of  the 
compreffing  power  of  the  blood,  and  likewife  of  the 
abforption  by  the  veins. 

DccccLxiii.  The  beginnings  of  decay  are  percep- 
tible even  in  youth  itfelf.  Even  in  that  blooming 
G g feafon 


LIFE. 


Chap.  XXS. 


feafon  the  folid  elements  of  the  body  are  augmented, 
the  apertures  through  which  the  humours  flow  are 
leflened,  the  veflels  are  obliterated,  and  the  greater 
attraction  of  the  cellular  fubflance  has  condenfed 
the  whole  body.  In  every  part  of  the  body  the  in- 
duration produced  by  age  becomes  confpicuous,  in 
the  bones  now  wholly  brittle,  in  the  Ikin,  in  the 
tendons,  in  the  conglobate  glands,  in  the  arteries, 
and  in  the  weight  of  every  part,  and  of  the  brain 
itfelf.  But  thoie  parts  grow  fooneft  rigid,  which  are 
moft  exercifed  by  motion  ; as  thofe  in  every  work- 
man, which  he  chiefly  employs  in  his  profeffion. 

DccccLXiv.  Moreover,  the  arteries  continue  to 
become  denfer,  narrower,and  even  impervious,  both 
by  the  internal  prefliire  of  the  blood  flowing  through 
the  large  arterial  tube,  and  by  the  attraction  of  the 
cellular  texture  of  which  the  greateft  part  of  the 
artery  is  compofed.  An  infinite  number  of  parts  of 
the  cellular  texture  therefore  ceafe  to  be  nourilhed  ; 
to  which  the  minute  arteries  hitherto  conveyed  nou- 
rifhment ; but  which  being  now  flopped  up,  bring 
none.  The  extending  force  being  removed,  the  cel- 
lular flocculi  attract  each  other,  leflen  the  interflices 
between  them,  degenerate  into  membranes,  or  fub- 
flances  of  a hard  texture,  which  inclofe,  and,  as  it 
were  flrangulate  other  veflels.  The  gelatinous  \"a» 
pour.likewife  concretes  in  the  interflices  of  the  cellu- 
lar texture,  and  forms  a hard  folid  with  its  fides.  The 
mufcles,  by  the  expulfion  of  their  blood,  and  the 
concretion  of  their  fibres,  degenerate  into  hard  denfe 
tendons,  deflitute  of  irritability. 

DccccLxv.  At  the  fame  time,  the  nerves  become 
more  and  more  callous,  and  infenfible  to  the  im- 
prefiions  of  the  fenfes,  and  the  mufcles  to  irritation  : 
thus  the  contractile  force  of  the  heart,  and  the  fre- 
quency of  its  pulfations,  is  diminiflied,  and  there- 
fore every  force  which  impels  the  blood  into  the 
ultimate  veflels. 


DC  CC  CL  XVI. 


LIFE. 


Chap.  XXX; 


467 


DccccLxvi.  The  quantity  of  humours  is  dimin- 
ifhed  in  the  denfer  body,  as  the  perlpiration,  femen, 
humours  of  the  eye,  and  of  the  conglobate  glands  ; 
the  vapour,  which  moiftens  the  folid  parts  of  the 
body,  every  where  manifeftly  decreafes.  For  this 
reafon,  nutrition  now  languifhes,  becaufe  there  is 
more  which  requires  nouriflxment,  and  lefs  nutri- 
tious juice. 

DccccLxvil.  Nor  is  the  quantity  of  humours  on- 
ly diminifhed : they  themfelveS  likewife  become  vi- 
tiated. They  were  mild  and  vifcid  in  children : 
but  thefe  fame  humours  are  now  acrid,  fait,  fetid, 
loaded  with  a great  quantity  of  earth,  in  old  men. 
This  is  produced  by  the  ufe  of  fait  and  putrefcent 
aliments,  the  bad  effects  of  which  increafe,  being 
collected  through  a great  length  of  time  ; alfo,  by 
the  diminution  of  the  cutaneous  perfpiration,  and 
the  coftivenefs  of  the  belly,  on  account  of  the  di- 
minifhed irritability,  and  by  the  reforption  of  the 
putrid  liquamen,  thus  increafed.  Hence  the  fetor 
of  the  urine,  of  the  breath,  and  the  difficult  healing 
of  wounds; 

DCcccLxviii.  But  the  greateft  fault  of  the  hu- 
mours, is,  that  they  abound  with  earthy  particles, 
both  collected  infenfibly  from  the  aliments  after  the 
fecretions  have  become  lefs  eafy,  and  partly  abftract- 
ed  from  the  folids  themfelves,  and  returned  into 
the  blood : for  this  earth  is  demonftrated  in  fome 
difeafes,  and  by  the  nature  of  the  gouty  concretions. 
From  this  abundance  of  earth,  the  proportion  of 
that  element  through  the  whole  body,  is  again  aug- 
mented, becaufe  the  nutritious  liquor  brings  too 
m.uch  of  it  along  with  it ; whence  the  brittlenefs  of 
the  bones,  and  the  hardnefs  of  all  the  parts  increaf- 
es  ; it  is  likewife  every  v/here  depofited  in  the  cel- 
lular texture,  and  produces  every  where  crufts,  at 
firft  callous,  and  then  bony  or  ftony,  chiefly  in  the 
coats  of  the  arteries. 

DccccLxix.  The  rigidity  of  the  whole  body,  the 
decreafe  of  the  mufcular  powers,  and  the  diminu- 
G G 2 tion 


DEATH. 


Chap.  XXX. 


468 

tion  of  the  fenfes,  conftitute  old  age  ; which,  fooner 
or  later,  opprefles  mortals  feverely  : fooner,  if  fub- 
jected  to  violent  labour,  or  addicted  to  pleafure,  or 
fed  upon  an  unwholfome  diet ; but  more  flowly,  if 
they  have  lived  quietly  and  temperately,  or  if  they 
have  removed  from  a cold  to  a warm  climate. 

Dccccnxx.  But  as  thofe  caufes  incelTantly  conti- 
nue to  operate  in  rendering  the  matter  of  the  body 
more  denfe,  in  diminifhing  its  irritability,  and  in 
augm.enting  the  quantity  of  earth,  it  is  not  polSble 
but  decrepit  old  age  muft  fucceed.  In  it,  the  fenfes 
are  almoft  deftroyed,  and  the*vis  infita  of  the  muf- 
cles  becomes  exceedingly  weak,  fo  that  the  limbs 
lofe  their  ftrength,  and  become,  efpecially  the  legs> 
unable  to  direct  the  body ; that  the  callous  infenfi- 
bility  of  the  nerves  cannot  be  excited  to  perform 
the  office  of  generation  ; that  the  very  inteftines, 
becoming  torpid,  do  not  obey  the  habitual  ftimuli ; 
that,  by  the  induration  of  the  intervertebral  carti- 
lages, the  body  bends  forward  ; that  by  the  falling 
out  of  the  teeth,  the  jaws,  now  rendered  fliorter, 
do  not  fupport  the  lips  fufficiently  ; and  laftly,  that' 
the  pulfations  of  the  heart  become  one  half  lefs  fre- 
quent than  in  the  infant  hate. 

DccccLxxi.  Thus  at  laft,  the  neceffity  of  natu- 
ral death  approaches,  although  the  greateft  number 
of  mortals  are  carried  off  prematurely  by  difeafes. 
One  in  a thoufand  exceeds  the  age  of  90  ; and  one 
or  two  perhaps  in  a century  live  to  the  age  of  150, 
Man  is  long  lived,  when  compared  with  other  ani- 
mals ; he  is  alfo  more  tender  than  any  of  them,  has 
loofer  flefh,  and  lefs  hard  bones.  It  is  not  eafy  to 
fay  what  was  the  caufe,  in  long  lived  people,  of 
their  longevity.  England  feems  to  exceed  all  other 
nations  in  the  number  of  thofe  who  live  to  an  ad- 
vanced age  ; and  in  general,  the  temperate  coun- 
tries are  remarkable  in  this  refpedt.  Among  the 
claiTes  of  men,  the  commonalty  has  almoft  folely 
afforded  thefe  rare  examples  j ^though,  irom  its 

being 


Chap.  XXX. 


DEATH. 


469 

being  the  moft  numerous,  we  may  expect  a greater 
number  of  examples.  Some  prerogative  feems  to 
belong  to  fobriety,  at  leafl  in  a moderate  degree  ; 
temperate  diet ; peaceable  difpofition  ; a mind  not 
endowed  with  very  great  vivacity,  but  cheerful,  and 
little  fubjed  to  care.  Among  animals,  birds  are 
longer  lived  : and  filhes,  whole  heart  is  very  fmall, 
growth  very  flow,  and  whofe  bones  never  harden, 
are  the  longeft  lived. 

DccccjLxxii.  Death  from  old  age  happens  fome-. 
times,  but  rarely.  It  may  be  faid  to  occur,  when 
the  powers  gradually  decay,  firft;  of  the  voluntary 
mufcles,  then  of  the  vital  mufcles,  and  laftly,  of  the 
heart  itfelf ; fo  that,  in  an  advanced  age,  life  ceafes 
through  mere  weaknefs,  rather  than  through  the' 
oppreflion  of  any  difeafe.  I have  often  obferved  the 
fame  kind  of  death  in  animals.  The  heart  becomes 
unable  to  propel  the  blood  to  the  extremities,  the 
pulfe  and  heat  defert  the  feet  and  hands ; yet  the 
blood  continues  to  be  fent  from  the  heart  into  thofe 
arteries  neareft  to  it,  and  to  be  carried  back  from 
thence : the  flame  of  life  is  thus  fupported  for  a 
little  while,  which  foon  after  we  perceive  to  be  ex- 
tinguifhed ; when  now  the  heart  itfelf,  being  totally 
deprived  of  its  powers,  and  not  irritable  by  the 
blood  to  any  effectual  motion,  cannot  propel  the 
blood  through  the  lungs,  that  the  aorta  may  receive 
its  due  quantity.  The  laff  efforts  of  refpiration  are 
now  exerted  to  open  a paffage  for  the  blood  through 
the  lungs,  until  even  the  powers  given  by  nature 
for  performing  the  aaion  of  infpiration,  becoming 
unequal  to  their  talk,  ceafe.  Then,  the  left  fide  of 
the  heart  neither  receives  blood  nor  is  irritated, 
and  therefore  remains  at  reft  ; while  yet,  for  a little 
time,  the  right  ventricle,  and  laftly  the  auricle  of 
the  fame  fide,  receive  the  blood  brought  by  the 
veins  from  the  cold  and  contracted  limbs,  and  being 
irritated  by  it,  continue  to  beat  weakly.  But  at  laft, 
when  the  reft  of  the  body  has  become  perfectly  cold. 


470  DEATH.  Chap.  XXX, 

and  the  fat  itfelf  congealed,  even  this  motion  ceafes, 
and  the  death  becomes  complete. 

DccccLxxiii.  I fliall  call  that  death,  when  the 
heart  has  become  totally  deprived  of  irritability. 
For  the  mere  quiefcence  of  the  heart  is  not  without 
hope  of  refufeitation  : neither  does  the  putrefaction, 
or  infenfibility,  or  coldnefs  of  any  part  of  the  ani- 
mal body,  demonftrate  the  death  of  the  whole  ani- 
mal : but  all  thefe  things,  when  joined  together, 
and  perpetually  increaiing,  with  the  rigidity  pro- 
duced by  the  congelation  of  the  fat,  in  confequence 
of  reft  and  cold,  afford  the  ftgns  of  death  in  any 
doubtful  cafe. 

DC cc CL XXIV.  The  body  after  death  is  deftroyed 
by  putrefaction.  Thus  the  fat,  and  the  w^ater,  and 
the  gluten,  being  refolved,  are  diflipated ; the  earth, 
deprived  of  its  bonds  of  union,  infcnftbly  moulders 
avray,  and  mixes  itfelf  wdth  the  duft.  The  foul 
goes  to  that  place  which  God  hath  appointed  it : 
its  indeftructibiiity  by  death  is  proved  by  a very 
common  phenomenon ; for  many  people,  when 
their  bodily  powers  are  w'^afted  and  fpent,  give  evi- 
dent proofs  of  a highly  ferene,  vigorous,  and  even 
cheerful  mind. 


INDEX. 


I N D 


E X. 


CHAP.  I. 

FIBRE.  CELLULAR  SUBSTANCE. 


I.  T^LEMENTARY  parts. 

Jlj  2.  General  ftru(Sture  of  the 
the  folids. 

3.  Fibres. 

Their  mofl:  fixed  particles  earthy. 

4.  The  earthy  particles  cohere  by 

means  of  interpofed  gluten. 

5.  Gluten  is  formed  of  oil  and  wa- 

ter. 

6.  Simple  fibres. 

7.  Vifible  linear  fibres. 

8.  Laminx. 

Cellular  Substance. 

9.  General  flrutSure  of  cellular  fub- 

llance. 

10.  Membranes,  vefibls,  t^d  tunics, 

are  formed  of  cellular  fub- 
ftance. 

II.  The  veflels  of  the  tunics  are  an 

acceffion  to  the  cellular  fub- 
Itance. 

12.  Cellular  fubftance  is  found  eve- 

ry where. 

13.  Inorganic  gluten. 

14.  Fibres  and  cellular  fubftance 

are  formed  of  gluten. 


15.  In  what  manner  the  folids  are 

formed  of  gluten. 

16.  Varieties  of  cellular  texture. 
Where  llrort  and  tender. 

17.  Where  lax. 

18.  The  fat  is  effufed  into  the  lat- 

ter. 

19.  The  fanguiferous  veffels  of  the 

cellular  fubftance. 

The  fat  is  depofited  by  the  ex- 
tremities of  the  arteries. 

It  alfo  exudes  through  their 
fides. 

20.  It  is  abforbed  by  the  veins. 

Do  nerves  terminate  in  the  cel- 
lular fubftance 

21.  All  the  cells  communicate  with 

each  other. 

22.  The  great  importance  of  cellu- 

lar fubftance  ? 

23.  The  contraiftility  of  cellular 

fubftance  is  different  from 
irritability. 

24.  The  various  ufes  of  fat. 

25.  The  caufes  and  effefts  of  the  ac- 

cumulation of  fat  in  the  cel- 
lular fubftaBce,  and  of  its  re- 
forption. 


CHAP. 


472 


INDEX. 


CHAP.  II. 
VESSELS. 


a6.  The  figure  of  the  arteries. 

27.  They  have  no  peculiar  and  con- 
ftant  external  membrane. 
Their  firft  true  membrane  is 
every  where  cellular. 
a8.  Externally,  this  is  more  lax,  and 
perforated  with  blood-velTels 
and  nerves. 

29.  Internally  it  is  more  denfe,  and 

forms  the  proper  coat  of  the 
artery. 

30.  The  mufcular  cojt  is  formed  of 

circular  fibres. 

There  are  no  longitudinal  ones. 
Under  the  mufcular  coat  there 
is  llrort  cellular  fubllance. 

31.  The  innermoft  membrane  of 

the  artery. 

Its  nature  in  the  arteries  of  the 
vifcera. 

32.  The  arteries  of  the  arteries. 

The  nerves  of  the  arteries. 

Do  they  derive  from  tliem  a 
contradllle  power,  different 
from  fimple  elaflicity  ? 

33.  The  fection  of  the  arteries  is 

round. 

The  pulfation  of  the  arteries. 

34.  T,rc  llrength  of  the  arteries. 
The  trunks  are  weaker,  and  the 

branches  ftronger. 

33.  Arteries  go  to  all  parts. 

The  proportion  of  arteries  to 
the  parts  which  they  fup- 
ply. 

36.  The  proportion  of  the  folid 

part  of  the  artery  to  its  cali- 
ber. 

37.  The  divifion  of  the  arteries  in- 

to branches. 

The  proportion  of  the  caliber 
of  the  branches  to  that  of 
the  trunk. 

The  angles  at  wliich  the  branch- 
es go  off. 


The  flexions  of  the  arteries. 

38.  The  anaftomofes  and  reticula^ 

dons  of  the  veflels. 

39.  The  tranfition  of  the  ultimate 

arteries  into  veins. 

40.  The  various  difpofition  of  the 

arteries  in  the  vifcera. 

41.  The  arteries  terminate  in  vef- 

fels  of  a fmalier  denomina- 
tion. 

42.  Or  in  excretory  dudls. 

43.  Or  in  exhaling  canals. 

44.  Are  veflels  every  where  pro- 

duced  from  the  red  ones  ? 

45.  Are  fmalier  orders  of  veffels 

produced  by  a multiplied  di- 
vifion ? 

46.  The  veins  are  fimilar  to  the  ar- 

teries in  many  rcfpecis,  but 
in  others  are  different. 

47.  The  ftruchire  of  the  veins. 

48.  The  fize  and  divifion  of  the 

veins. 

They  affedt  the  furface  of  the 
body. 

49.  The  valves  of  the  veins. 

50.  The  veins  originate  from  arte^ 

ries ; from  veins  of  inferior 
orders ; from  the  abforbing 
veins  of  the  w’hole  circumfe- 
rence, and  of  every  cavity  of 
the  body. 

51.  Other  abforbing  veffels  from 

the  cellular  texture  are  little 
diflerent  from  thefe. 

5 2.  There  are  veins  as  well  as  arte- 
ries of  fmalier  kinds. 

53.  The  IjTnphatic  veffels. 

J4.  The  conglobate  glands. 

55.  Where  the  lymphatic  veffels  are 
found. 

They  unite  in  the  thoracic  du<2. 
36.  The  office  of  the  conglobate 
glands. 

57.  The  valves  of  the  lymphatics. 


CILM-. 


INDEX. 


All 


CHAP.  III. 


CIRCULATION,  or  the  MOTION  of  the  BLOOD 
THROUGH  THE  ARTERIES  ANB  VEINS. 


j8.  In  what  manner  the  blood  fills 
the  arteries  and  veins. 

59.  The  blood  moves  rapidly 

through  all  the  veflels. 

60 — 76.  The  diretStion  of  the  mo- 
tion of  the  blood. 

60.  Proofs  that  all  the  arteries  and 

veins  communicate. 

61.  The  bloopd  flows  through  the 

arteries  from  the  heart  to  the 
extremities. 

,6a.  The  motion  of  the  venous  blood 
was  doubted. 

Who  have  difcovered  their  er- 
ror. 

63.  Harvey  firfl  fliowed,  that  the 

venous  blood  every  where 
returned  from  the  extremi- 
ties to  the  heart. 

This  is  proved  by  the  valves 
which  prevent  the  reflux  of 
the  blood  into  the  branches. 

64.  The  valves  alfo  fuftain  the 

weight  of  the  blood. 

They  alfo  caufe  the  prefTure  of 
the  mufcles  upon  the  veins 
to  diredt  the  blood  towards 
the  heart. 

65  — 70.  Proofs  of  the  courfe  of 
the  venous  blood. 


63.  The  valves  of  the  right  fide  of 
the  heart. 

66.  Ligatures  and  compreflion  in  a 

living  perfon. 

67.  More  accurate  experiments  on 

living  animals. 

68.  InjetSlions  into  the  veins. 

69.  Transfufion  of  blood. 

70.  InjeeSHons  prove,  that  the  blood 

palTes  from  the  arteries  into 
the  veins. 

71.  The  fame  paflage  is  lliown  by 

the  microfeope. 

There  is  no  parenchyma  be- 
tween the  arteries  and  veins. 

72.  The  nature  of  that  circulation 

of  the  blood,  which  is  prov- 
ed by  what  is  already  faid. 

73.  There  are  inftances,  however, 

where  the  palTage  is  for  a 
little  in  a contrary  diretSllon. 

74.  In  the  lymphatic  velTels  the 

courfe  of  the  liquor  is  from 
their  roots  to  the  thoracic 
du(fi. 

73.  The  reforbed  vapours  are  car- 
ried tow'ards  the  heart. 

76.  A palTage  muflbe  found  for  the 
blood  from  the  right  ventri- 
cle of  the  heart  into  the  left. 


C H:,A  P.  IV, 


HEART. 


77,  78.  The  bags  of  the  pleura. 

77.  The  mediaftinum. 

The  pleura. 

78.  The  fituation  of  the  pericardi- 

um. 

The  mediaftinum  pofterius. 

The  ligaments  of  the  lungs. 

79.  80.  The  pericardium. 

81.  The  arteries  of  the  pericardi- 
um. 

Its  veins. 

Herves. 


82.  The  ftrutfture  of  the  pericardi- 

um. 

The  water  contained  in  it. 

83.  The  ufe  of  the  pericardium. 

84.  What  animals  have  a heart. 

83.  In  what  manner  the  vena  cava 

terminates  in  the  heart. 

86.  The  right  finus  venofus. 

The  right  auricle. 

87.  The  foflaovalis. 

The  anulus  ovalis. 

88.  The  valve  of  Euftachius. 

89.  By 


INDEX. 


47^ 

89.  By  what  powers  the  blood  is 

forced  into  the  right  porch 
of  the  heart. 

90.  The  contratftion  of  the  right 

auricle,  and  its  effedls. 

91.  The  figure  and  fituation  of  the 

heart- 

9a.  The  anterior  or  right  ventricle 
of  the  heart. 

93.  The  valvulae  triglochines. 

94.  Their  papillary  mufcles. 

95.  The  ufe  of  the  triglochines. 

96.  The  heart  is  IHmulated  to  con- 

fra<Tion,by  the  blood  thrown 
into  it. 

97.  The  mufcular  fibres  of  the  heart, 

according  to  the  author. 

98.  The  fame  deferibed  by  others. 

99.  The  nerves  of  the  heart. 

XQO.  Thefe  nerves  contribute  to  the 
motion  of  the  heart. 
lOl.  There  is,  however,  fome  other 
caufe. 

loa.  The  irritability  inherent  in  the 
heart. 

103.  How  the  contraction  of  the 
ventricle  is  performed. 

X04..  Bythe  contradtion  ofthe  heart, 
the  blood  does  not  return 
into  the  auricle  and  veins. 

105.  By  the  contradlion  of  the  right 

ventricle  the  blood  is  driven 
into  the  pulmonary  artery. 

106.  The  origin  and  beginning  of 

the  pulmonary  artery. 

Its  femilunar  valves. 

107.  The  pafl'age  of  the  blood  from 

the  right  ventricle  into  the 
pv.hnohary  artery. 

3c8.  The  palTage  of  the  blood 
through  the  lungs. 

109.  The  blood  cannot  retvrm  from 
the  pulmonary  artery  into 
the  heart. 

no.  The  pulmonary  veins. 

The  courfeof  the  bloodthrough 
thefe. 

III.  The  left  fmus  venofus. 

The  left  auricle. 

1 1 3.  The  contradlicn  of  the  left 
porch  forces  the  blood  into 
the  left  ventricle. 

The  valvulx  mitralcs. 

113.  The  courfc  of  the  blood  from 
the  right  ventricle  into  the 
left,  or  the  fmaller  circula- 
tion. 

114-  The  left  ventricle. 


1 15.  The  blood  is  forced  info  the 

aorta  by  the  contraiTion  of 
the  left  ventricle. 

116.  The  valves  of  the  aorta. 

1 1 7.  The  diaftole  of  the  heart, 

118.  In  what  manner  the  motions 

of  the  auricles  and  ventricles 
alternately  follow  one  anoth- 
er. 

119.  “Why  are  thefe  motions  contin- 

ued fo  long,  and  fin  conllantly. 

120.  This  quefbon  is  explained,  by 

the  Ibmulus  of  the  blood 
driven  into  irritable  ca\T- 
ties. 

121.  Nothing  more  is  necellary. 
The  realbn  cannot  be  found 

cither  in  the  comprcllion  of 
the  nerves,  or  in  the  corona- 
ry arteries. 

122.  The  powers  of  the  heart  are 

not  aflilled  by  the  ofcillation 
of  the  ultimate  vcflcls. 

Or  by  the  power  of  external 
heat. 

Or  by  the  contradtilc  force  of 
the  arteries. 

123.  The  velocity  with  which  the 

blood  ilTues  from  the  heart. 
The  weight  of  the  blood  in- 
cumbent on  the  heart. 

The  force  of  tlie  heart. 

124.  Many  things  on  tliis  fubjedt 

are  uncertain. 

The  powers  of  the  heart  are, 
however,  very  flrong. 

125.  This  is  proved  by  the  refinan- 

ces which  the  heart  over- 
comes. 

126.  The  entrance  of  the  blood  in- 

to the  coronary  arteries. 
Tbe  two  coronary  arteries. 

127.  They  terminate  in  veins. 

I nc  great  coronary  vein. 

128.  The  middle  veiu. 

The  third  vein. 

129.  The  anteri.>r  veins. 

130.  The  middle  lized  veins. 

131.  The  minute  veins. 

132.  At  what  time  the  coronary  ar- 

teries receive  the  blood. 

133.  The  blood  returns  from  the 

coronary  arteries  into  the 
cavities  of  the  heart  through 
the  veins. 

134.  The  hmipliatic  veflcls  of  the 

heart. 


CH-\P. 


INDEX. 


47S 


CHAP.  V. 

NATURE  OF  THE  BLOOD,  and  HUMOURS  of  ths 
HUMAN  BODY. 


135.  The  blood  in  general. 

136.  The  warmth  of  the  blood. 

The  halitus  ifTuing  from  blood 

when  drawn. 

137.  The  blood  coagulates  when 

the  halitus  is  difcharged. 
The  cruor  is  the  principal  part 
of  the  coagulum. 

138.  The  ferum  of  the  blood. 

139.  How  the  blood  is  changed  by 

putrefaction. 

140.  Befides  thefe,  there  are  in  the 

blood,  fea-falt,  earth,  calx  of 
iron,  and  air  in  an  inelaflic 
Hate. 

141.  What  changes  are  produced 

in  the  blood  by  the  admix- 
ture of  halts.  • 

14a.  The  chemical  analyfis  of  the 
blood. 

143.  Refult  of  the  information  de- 

rived from  it. 

144.  Red  globules  are  diftinguiflied 

in  the  blood  by  the  help  of 
the  microfcope. 

Their  figure. 

145.  The  colour  of  the  globules, 

their  number,  magnitude, 
and  variable  figure. 

Do  they  break  down  into  oth- 
« er  fmaller  globules  ? 

146.  Fibres  are  produced  from 

waflied  blood,  which  did  not 
exift  in  the  living  animaL 


147.  The  cruor  is  compofed  of  glo- 

bules, which  are  inflamma- 
ble. 

148.  The  chemical  analyfis  of  the 

ferum. 

The  aqueous  humours,  the  fal- 
iva  and  mucus,  afford  near- 
ly the  fame  prodiuEts. 

149.  The  quantity  of  blood  in  the 

whole  body. 

ijo.  The  proportions  of  the  ele- 
ments of  the  blood  are  not 
always  the  fame. 

The  caufes  which  vary  tlieiy 
proportion, 

151.  On  the  different  proportion  of 
the  elements,  and  the  coa- 
fidcration  of  the  ftrudlure  of 
the  folids,  depend  the  differ- 
ences of  temperaments. 

Tja.  The  ufe  of  the  red  cruor. 

1J3.  The  coagulable  ferum,  thinner 
liquids,  faline  particles,  air 
and  fire ; the  effeCls  of  each. 

154.  The  thick  blood  and  more 

thin  liquids  are  equally  ne- 
ceffary  for  health. 

155.  The  difference  between  the  ar- 

terial and  venous  blood. 

156.  All  the  reft  of  the  humours  are 

produced  from  the  . bloo4 
alone. 


CHAP.  VI. 


COMMON  FUNCTIONS  of  the  ARTERIES. 


157.  The  blood  propelled  from  the 

left  ventricle  into  the  aorta. 

158.  The  arteries  are  conftantly 

full. 

The  pulfation  of  the  arteries, 
and  its  caufe. 

3:59.  The  contraction  of  the  arte- 
ries. 


160.  How  is  it  proved  that  the  ar- 

tery is  contracted,  and  tha^ 
the  blood  is  driven  forwards 
by  that  means  ? 

161.  No  fucceffion  can  be  perceiv- 

ed in  the  pulfation  of  differ- 
ent arteries,  although  we  arc 


certaia 


INDEX, 


475 


l6j. 


163. 

164. 
163. 

z66. 


167. 


j68. 


J69. 

X70. 

>71- 


188. 

189. 


certain  that  it  ac);ully  takes 
place. 

The  velocity  of  the  blood 
coming  from  the  heart  muft 
continually  be  diminillied  as 
it  proceeds  farther  through 
the  arteries. 

What  circumltance's  feem  to 
diminilli  its  velocity,  with- 
out adlually  diminilliing  it. 

The  blood  does  not  feem  to 
lofe  fo  much  of  its  velocity 
as,  according  to  calculation, 
it  ought  to  do. 

The  caufes  of  this. 

Why  the  pulfe  vaniflies  in  the 
ultimate  arteries. 

The  blood  prefTes  againfl;  the 
fides  of  the  veins. 

W'’hy  the  veins  do  not  beat  like 
the  arteries. 

The  pall'e  is  the  meafure  of  the 
powers  of  the  heart. 

What  is  meant  by  a flow,  full, 
hard,  or  quicjc  pulfe. 

Where  it  is  bcft  felt. 

The  pulfe  is  flower  in  propor- 
tion to  the  bulk  of  the  ani- 
mal. 

The  diflTerence  of  the  pulfe  in 
men,  according  to  the  time 
of  the  day. 

A frequent  pulfe  is  dilFerent 
from  a quick  one. 

DiflTerent  caufes  of  a frequent 
pulfe. 

By  what  powers  the  venous 
blood  is  moved. 

It  moves  more  quickly  in  the 
trunks  than  in  the  branches. 

By  what  means  the  blood  is 
prevented  from  flagnating 
and  coagulating  in  the  veins. 


171.  The  venous  blood  is  propelled 
by  the  aAion  of  the  muf- 
cles. 

173.  Other  powers  comprefling  the 

veins. 

174.  The  power  of  derivation. 
What  are  the  efFedb  of  anaf- 

tomofes. 

175.  The  velocity  of  the  venous 

blood. 

What  caufes  render  its  motion 
s more  difEcult. 

176.  The  time  in  which  the  circu- 

lation is  performed. 

177.  The  efFedts  of  the  motion  of 

the  heart  and  arteries  upon 
the  blood,and  by  what  means 
they  are  eftimated. 

178.  179.  The  means  bv  which  we 

underftand  the  manner  in 
which  thefe  clTedls  are  pro- 
duced. 

180.  The  fridtion  which  takes  place 
in  the  arteries. 

Its  efledts,  how  calculated. 
Whence  the  rednefs  of  the 
blood. 

18  r.  Does  the  heat  of  the  blood 
arife  from  its  motion  f 
1S2.  The  progreflive  motion  of  the 
blood  hinders  putrefadlion. 

183.  It  is  various  in  different  parti- 

cles of  different  natures. 

184.  The  effedts  of  the  fyftole  of  the 

arteries. 

185.  The  fmallcft  mouths  of  the  ar- 

• tcries  arethemouldsinwhich 

the  particles  of  blood  are 
formed.  • 

186.  WTat  is  the  ufe  of  the  reticu- 

lations of  the  arteries. 

187.  The  cffedls  of  a retarded  mo- 

tion of  the  bhiod. 


CHAP.  VII. 


SECRETION. 


Four  clalTes  of  fecreted  hu- 
mours. 

The  fird  confifls  of  the  coagu- 
iable  ones,  which  for  the 
moft  part  exhale. 

The  fecond  are  not  coagulable, 
and  partly  exhale,  and  part- 
ly do  not. 


The  third  are  mucous. 

The  fourth  inflammable. 

The  other  humours  are  com- 
pofed  of  thefe. 

A defeription  of  the  fecretorv 
organs  is  required,  in  order 
to  Jifeover  the  reafen  of  the 

diverhty 


190. 

191. 
19a. 

193- 


INDEX. 


diverlity  of  the  fecreted  flu- 
ids in  the  different  organs. 

194.  The  fecretion  of  coagulable 

liquors  is  performed  with- 
out glands. 

195.  What  glands  fecrete  the  albu- 

minous fluid  of  the  joints. 

196.  The  feat  of  thefe  glands. 

197.  The  exhaling  liquors  which  are 

not  coagulable  are  fecreted 
without  glands. 

198.  Such  liquors  as  are  neither  co- 

agulable nor  exhaling,  are 
fecreted  by  conglomerate 
glands. 

Thefe  are  compofed  of  acini. 

199.  aoo,  201.  The  flrudture  of  thefe 

acini. 

202.  Some  liquors  of  the  nature  of 
198  are  even  fecreted  with- 
out thefe  kernelly  glands. 

303.  The  mucus  is  every  where  fe- 

creted by  glands. 

The  ftrudfure  of  a true  gland, 

304.  How  the  fecretion  is  perform- 

ed in  thefe  glands. 

30J.  The  excretory  orifices. 

The  cryptJE. 

306.  The  conglutinated  glands. 

207.  The  excretory  dudfs. 

308.  The  compound  glands. 

The  agminated  or  congregate 
glands. 

309.  The  various  fecretlons  of  In- 

flammable liquors. 

There  are  many  febaceous 
glands  without  a dudh 

310.  Other  febaceous  ones  have  a 

dudh 

31 1.  Compound  febaceous  ones. 

212.  The  milk  is  fecreted  in  con- 

glomerate glands. 

313.  The  organs  being  deferibed, 

we  return  to  the  queftion 

193- 

314.  The  blood  going  to  the  fecre- 

tories  is  already  of  a partic- 
ular nature. 

213.  The  retardation  of  the  blood 

in  the-  minute  veffels  fepa- 
rates  the  more  denfe  hu- 
mours from  thofe  that  are 
lighter  and  more  fluggidi. 
216.  The  mouths  of  the  fecretory 
veffels  are  of  very  different 
diameters. 

317.  This  inequality  may  alter  the 


All 

fecretlons  in  many  different 
ways. 

318.  Mofl  fecretlons  are  performed 

by  veffels  arifing  from  fan- 
guiferous  arteries. 

Others,  however,  by  veffels 
which  arife  from  an  inferior 
order  of  arteries. 

319.  The  angle  at  which  the  fecre- 

tory branch  goes  off  is  per- 
haps of  fome  confequence. 
What  things  render  this  pro- 
bable. 

What  things  render  it  doubt- 
ful. 

220.  The  flexions  of  veffels  contri- 
bute to  fecretion. 

321.  The  denfity  of  the  arteries 
may  do  the  fame. 

Their  irritability  has  nearly 
fimilar  effedts. 

222.  Various  circumflances  which 
augment  or  diminifli  the  ve- 
locity of  the  blood  have  great 
effedi  on  the  fecretlons. 

323.  The  fecreted  humours  are  va- 
ried by  a variation  of  thefe 
conditions. 

224.  The  largefl  and  denfeft  parti- 

cles of  the  blood  pafs  into 
the  veins. 

225.  What  becomes  of  the  large, 

flow,  and  fluggifh  particles. 
And  of  the  coagulable  ones. 

226.  In  what  veffels  the  thin  and 

aqueous  liquors  are  fecreted. 
In  what  veffels  the  light  aque- 
ous but  vifeid  and  flow  hu- 
mours. 

327.  Various  hypothefes  are  form- 
ed concerning  fecretion. 

228.  It  remains  to  be  difeovered 
how  the  pure  fecretlons  arc 
made. 

AJl  recent  fecretlons  have  au 
admixture  of  water. 

329.  All  of  them  become  vifeid  by 
flagnating  in  follicles. 

230.  The  fluids  may  be  changed  in 
their  receptacle  by  the  ad- 
mixture of  a new  liquid. 

331.  The  reforbed  humours  are  al- 
fo  of  life. 

232.  The  ufe  of  receptacles. 

233.  The  powers  by  which  the  re- 

tained humours  are  at  laft 
ejedted. 

CHAP, 


INDEX. 


CHAP.  VIII. 
RESPIRATION. 


234.  Tlie  figure  of  the  lungs. 

335.  The  external  membrane  of  the 
lungs. 

236.  The  firucture  of  the  lungs. 

237.  The  flrudlure  of  the  afperia 

arteria. 

238.  Its  mufcular  fibres. 

239.  Its  mucous  glands. 

The  conglobate  glands  conti- 
guous to  it. 

240.  The  veffels  and  nerves  of  the 

afperia  arteria. 

341.  Its  divifion  into  bronchia. 

342.  Their  ultimate  branches  ter- 

minate in  cellular  texture. 

343.  The  bronchial  arteries  & veins. 

244.  The  pulmonary  artery. 

The  pulmonary  veins. 

245.  The  lymphatic  vefl'cls  of  the 

lungs. 

The  nerves  of  the  lungs. 

346.  A very  large  portion  of  the 
blood  enters  the  lungs. 

The  utility  of  this  vifeus  de- 
pends on  the  air. 

247.  The  nature  of  atmofpherical 

air. 

248.  In  what  manner  it  is  excluded 

from  the  body. 

We  muft  invelligate  why  it 
enters  the  lungs. 

349.  The  reafon  why  it  enters  them. 

250.  The  general  fabric  of  the  tho- 

rax. 

251.  The  vertebrx  of  the  back. 
2J2.  The  articulation  of  the  ribs 

with  the  vertebrae. 

The  ligaments  of  this  articula- 
tion. 

253.  How  the  ribs  are  joined  with 
the  fternum. 

334.  The  length  of  the  ribs. 

235.  The  direction  of  the  ribs. 
Their  Ilrength  various. 

236.  The  fternum. 

237.  The  thorax  muft  be  raifed  in 

order  to  dilate  the  feat  of 
the  lungs. 

This  is  performed  by  the  ex- 
ternal intercoftal  mufcles. 


238.  The  internal  intercoftals. 
There  are  doubts  concerning 

the  aiStion  of  thefe,  but  it  is 
certain  that  they  elevate. 

239.  In  what  manner  the  thorax  is 

enlarged  by'  thefe. 

But  tins  dilation  is  not,  how- 
ever, fufticient. 

260,  261.  The  diaphragm. 

262.  The  two  holes  of  the  dia- 

phragm. 

263.  The  contradlion  of  the  fep- 

tum  augments  the  capacity 
of  the  thorax. 

Alone,  it  almoft  performs  reC- 
piration. 

264.  By  what  powers  it  is  aflifted 

in  deep  infpirations. 

263.  Infpiration,  how  performed. 

Its  efl'ccls  on  the  air  and  blood- 
veflels. 

266.  Is  air  contained  between  the 

lungs  and  thorax  ? 

267.  The  air  is  vitiated  by  refpifa- 

tion. 

268.  The  inconvenienciesof  too  long 

an  infpiration. 

269.  The  powers  of  expiration. 

270.  The  abdominal  mufcles  con- 

fpire  to  produce  this  cffeift. 
The  fternocoftals  and  others 
alfo  alllft. 

271.  What  powers  afllft  the  muf- 

cles in  ftronger  refpirations. 

272.  The  effeifts  of  expiration. 

273.  From  thence  there  arifes  a 

new  nccellity  for  infpiratu.n. 

274.  Other  caufes  for  alternate  ref- 

plritioD  are  fcarcely  afeer- 
tained. 

273.  Refpiration  is  neceffary  for 
adults. 

276.  The  utility'  of  refpiration  is 

different  from  that  necelEty. 

277.  How  that  is  afccrt.iined. 

278.  Is  heat  generated  in  the  lungs  ? 

279.  Is  the  blood  coadenfed  in  the 

lungs  ? 

280.  Is  the  air  itfclf  received  into 

the  blood  in  the  lungs  ? 

What 


INDEX. 


479 


What  clrcnmftances  render 
this  probable. 

s8x.  What  I'eem  to  prove  the  con- 
trary. 

%%%.  Is  the  blood  cooled  in  the  lungs? 

485.  Does  the  red  colour  of  the 
blood  proceed  from  the  air? 

285.  Is  the  ufe  of  the  blood  to  ab- 
forb  nitre  from  the  air  ? 

485.  What  animals  live  long  v/ith- 
out  air. 

Why  every  animal  dies  in  air 
that  is  not  renewed. 


287.  What  is  the  conhecflon  be- 

tween the  puife  and  refpira- 
tion. 

288.  Cough. 

289.  Laughter. 

Weeping. 

Hickup. 

Sneezing. 

290.  The  acceflbry  ufes  of  refpirai 

tion. 


CHAP.  IX. 


VOICE  AND  SPEECH; 


4§S.  The  larynx  is  compofed  of  car- 
tilages. 

Its  veffels  and  nerves. 

292.  The  fcrutiform  cartilage. 

293.  The  annular  cartilage. 

294.  The  arytenoid  cartilages. 

295.  The  glottis. 

296.  The  epiglottiE. 

297.  The  ventricles  of  the  larynx. 

298.  The  mucous  glands  of  the  la- 

rynx. 

299.  The  thyroid  gland. 

36b.  The  connedtion  of  the  larynx 
with  the  os  hyoides. 

The  elevation  of  the  larynx, 
and  contradlion  of  the  glot- 
tis. 


joi.  The  depreffion  of  the  larynf:^ 
and  dilatation  of  the  glottis. 

302.  The  cavity  of  the  mouth. 

The  noftrils. 

303.  The  tongue. 

304.  The  voice. 

Whifpering. 

305.  The  ftrength  of  the  voloe. . 
What  circumflances  produce 

an  acute  tone. 

306.  A grave  tone  is  produced  by 

the  oppofite  caufes. 

307.  The  caufes  of  diverfity  of  tone. 

308.  Singing. 

309.  Speech. 

310.  The  pronunciation  of  letters. 


CHAP.  X. 

BRAIN  AND  NERVES. 


311.  The  nature  of  the  arrange- 

ment. 

312 — 319.  The  arteries  which  be- 
long to  the  brain. 

312.  The  arch  of  the  aorta,  and  the 

branches  produced  from  it, 

313.  The  diviiion  of  the  carotid. 
The  external  carotid.  From 

it  proceeds. 

The  fuperior  thyroid  artery. 
The  lingual. 

The  labial. 

The  afeeading  pharyngea. 


314.  The  occipital  artery. 

The  auricular. 

315.  The  temporal  artery. 

The  internal  maxillary. 

The  principal  branch  to  the 
dura  mater. 

Other  branches  of  the  internal 
maxillary. 

316.  The  internal  carotid. 

Its  flexures. 

Its  paffage  through  the  fora- 
men of  the  os  petrofum. 


The 


4S0 


INDEX, 


Tlie  branches  produced  from 
it  in  the  receptacle. 

317.  The  branches  of  the  internal 

carotid  on  the  bridge  and 
crura  of  the  brain. 

Tire  branch  to  the  plexus  cho- 
roides,  and  accompanying 
the  optic  nerve. 

The  anterior  and  poflerior 
branch. 

The  (IrniElure  of  the  branches 
of  the  carotid  artery  which 
be  within  the  fkull. 

318.  The  vertebral  artery. 

The  bafilaris. 

The  profunda  cerebri. 

319.  The  conclulions  which  may  be 

deduced  from  the  hiftory  of 
the  arteries  of  the  brain. 

320 — 324.  The  coverings  of  the 
brain. 

320.  The  ofleous  fhell  of  the  ence- 

phalon. 

The  dura  mater  in  general. 

321.  The  external  and  internal  la- 

mina of  the  dura  mater. 

The  falx  and  tentoria  proceed 
from  thefe ; their  ufe. 

322.  The  glands. 

323.  The  arachnoid  membrane. 

324.  The  pia  mater. 

325 — 339.  The  veins  of  the  ence- 
phalon. 

325.  The  fourth  finus. 

326.  The  fuperior  finus  of  the  falx. 
The  tranfverfe  finufes. 

327.  The  inferior  finus  of  the  falx. 

328.  The  inferior,  anterior,  and  pof- 

terior  veins  of  the  brain. 

329.  The  veins  of  the  cerebellum. 
The  fuperior  veins  terminate 

in  the  fourth  finus  ; the  in- 
ferior ones  in  the  fuperior 
petrous  andtranfverfe  fiauf- 
es. 

530.  Circular  finus. 

The  tranfverfe  finus  joining 
the  cavernous  ones. 

331.  ‘The  fuperior  finus  petrofus. 

The  inferior  finus  petrofus. 
The  pofierior  occipital  finus. 

332.  The  anterior  occipital  finus. 
The  cavernous  finus. 

The  conjundlion  of  the  finufes 
and  external  veins  of  the 
cranium  with  each  other, 
and  its  eiFetSfs. 


333.  The  ufe  of  the  finufes. 

334.  The  connedlion  between  the 

arteries  and  the  finufes. 

335.  The  blood  chiefly  flows  into 

the  jugular  veins. 

Their  cerebral  and  facial 
branches. 

336.  The  external  jugular  vein. 

The  internal  vertebral  vein. 

337.  The  finufes  of  the  medulla  fpi- 

nalis. 

338.  The  iifes  of  the  venous  anafto- 

mofes. 

339.  The  l)'mphatic  vefTels  of  the 

brain. 

The  reforption  of  what  is  ex- 
haled in  the  brain. 

340.  A great  number  of  parts  are 

comprehended  under  the 
name  of  encephalon. 

The  cerebrum,  cerebellum, 
bridge,  and  medulla  oblon- 
gata, what  they  are. 

341.  The  figure  of  the  brain. 

Its  circumvolutions. 

— cortex. 

— ^medulla. 

— lobes. 

342.  The  minute  ftruclure  of  the 

brain. 

343 — 53.  The  interior  anatomy  of 
the  brain. 

343.  The  oval  fecHon  of  the  brain. 
The  corpus  callofum. 

344.  The  anterior  or  three-horned 

ventricle. 

345.  The  corpora  ftrlata. 

The  thalami  of  the  optic 
nerves. 

The  double  femicircular  cea- 
tre.  ^ 

The  anterior  comminure. 

The  mamillary  eminences. 

346.  The  pellucid  feptum. 

The  fornix. 

The  fimbria:. 

The  hippocam.pi. 

The  pfalterium. 

347.  The  choroid  plexus. 

348.  The, third  ventricle. 

349.  The  pituitary  gland. 

3jO.  The  poflerior  double  commif- 
fure. 

351.  The  ftparat'on  of  the  third 
ventricle  from  the  calamus 
feriptorius. 

The  anterior  commiiTure. 

2Si.  The 


INDEX.  481 


5J2.  The  nates. 

The  teftes. 

The  pineal  gland. 

S53.  The  crura  of  the  brain. 

354.  Tlie  cerebellum. 

3J5.  The  bridge. 

The  medulla  oblongata. 

The  olive  fhaped  and  pyrami- 
dal bodies. 

The  fourth  ventricle. 

The  great  valve. 

The  aquedudt. 

The  calamus. 

356.  The  common  properties  of  the 

nerves  of  the  brain. 

357.  The  origins  of  each  of  the 

nerves  of  the  brain. 

358.  The  medulla  fpinalis. 

Its  pia  mater,  arteries,  and 
veins. 

359.  The  arachnoid  membrane  of 

the  medulla  fpinalis. 

360.  The  hard  membrane  of  the 

medulla  fpinalis. 

The  denticulated  ligament. 

361.  The  common  properties  of  the 

fpinal  nerves. 

362.  The  anterior  and  poflerior 

trunks  of  the  fpinal  nerves. 
The  intercoftal  nerve. 

^'he  eighth  pair. 

The  phrenic  nerve. 

The  acceflbry  nerve. 

364.  The  extremity  of  the  nerves. 
The  ftraightnefs  of  the  fibres 

of  the  nerves. 

The  nerves  are  fcarcely  elafr 
tic,  and  not  at  all  irritable. 
The  number  of  nerves  is  iri 
proportion  to  the  parts  to 
which  they  are  fent. 

The  anaftomofes  of  the  nerves. 
Ganglions. 

365.  How  it  is  proved  that  fenfa- 

tlon  is  owing  to  the  nerves. 
It  is  the  medullary  part  of  the 
nerve  which  feels. 

366.  The  foul  perceives  in  the  brain; 

not  immediately  by  the  fen- 
foria  and  branches  of  the 
nerves. 

367.  How  the  mufcles  are  affedted 

by  compreffing  or  irritating 
the  nerves. 

368.  What  derangements  of  the  an- 

imal motions  happen  on  in- 

Hh 


juring  the  brain  or  fpinal 
marrow. 

369.  From  what  is  laid  down  in. 

367  and  368,  the  nerves  are 
proved  hkewife  to  be  the 
organs  of  motion. 

370.  Is  there  in  the  brain  any  prin- 

cipal feat  in  which  is  the 
origin  of  all  motions,  and  the 
end  of  all  fenfatioh,  where 
the  foul  reftdes  ? 

It  is  not  in  the  corpus  callo- 
fum. 

371.  Neither  is  it  the  proper  prov- 

ince of  the  cerebellum  to 
carry  on  the  vital  motions. 
Nor  are  the  motions  called 
animal  and  vital  to  be  refer- 
red to  different  fources. 

372.  The  feat  of  the  foul  is  where 

the  nerves  firft  begin. 

373.  The  nerves  are  the  organs  of 

fenfation  and  motion,  not 
by  their  membranes,  but  by 
their  medullary  part. 

374.  What  the  medulla  is. 

21 S-  Whether  the  medullary  fibres 
are  folid. 

376.  The  nerves  are  entirely  devoid 

of  elaflicity.  ' 

377.  Motion  can  only  be  propagat- 

ed downwards. 

From  what  is  faid,  it  follows, 
that  the  medullary  fibre 
feems  to  be  hollow. 

378.  Refutation  of  the  objedlions 

againft  this. 

379.  The  nature  of  the  nervous  flu- 

id. 

Hov/  proved  not  to  be  elec- 
trical. 

380.  The  nature  of  that  fluid  is  nei- 

ther aqueous  nor  albuminous. 
3S1.  Of  what  kind  the  nervous  flu- 
id ought  to  be. 

382.  How  it  is  rendered  more  pro- 

bable that  the  nervous  fluid 
pafl'es  through  hollow  tubes 
than  through  the  fpongy  and 
folid  fubftance  of  the  nervu. 

383.  The  motion  of  the  nervous 

juice  is  twofold. 

384.  The  fame  nerves  moft  evident- 

ly ferve  both  for  feufe  and 
motion. 


38J.  What 


r 


4S2 


INDEX. 


385.  what  becomes  of  the  nervous 

fluid. 

Whether  it  nouriflies. 

386.  Qucftions  concerning  the  ufes 

of  the  parts  of  the  brain. 

387.  The  offices  of  the  ventricles. 


388.  What  is  known  concerning  th< 

ufe  of  the  tubercles. 

389.  The  offices  of  the  ftriae  and  of 

the  internal  du<£b. 

390.  The  reafon  for  the  arrange- 

ment of  wliat  follows. 


CHAP.  XI. 

MUSCULAR  MOTION. 


391.  The  dead  power  of  the  fibre. 

392.  'I'he  reafon  why  it  is  called 

dead. 

Its  effehbs. 

393.  The  characters  of  the  dead 

power. 

The  charadlers  which  arc  pe- 
culiar to  the  red  mufcular 
fibre. 

It  is  necefifary  to  examine  its 
ftrudlure. 

394.  What  nuifculaf  fibres  and  muf- 

cles  are. 

393.  The  fibres  treated  more  fully. 

396.  The  belly,  tendon,  aponcuro- 

lis,  and  capfule  of  a mufcle, 
what. 

Whether  the  fibres  of  the  ten- 
dons are  of  a dilFerent  genus 
from  the  mufcular  fibres. 
Mufcles  which  commonlyhave 
no  tendons. 

The  parts  in  which  the  muf- 
cles chiefly  terminate  in  long 
tendons,  and  thofe  to  w'hich 
they  affix  themfelves. 

397.  The  modes  in  which  the  ten- 

dons unite  themfelves  with 
the  flelh. 

A pmnated  mufcle,  what. 

398.  The  arteries,  veins,  h-mphat- 

ics,  and  nerves,  of  the  muf- 
cles. 

399.  The  fcrudlure  of  the  ultimate 

fibre,  which  is  the  elementa- 
ry part  of  the  mufcle. 

400.  There  is  a threefold  force  in 

the  mufcle. 

The  vis  infita  of  the  mufcle. 

401.  The  meafure  of  the  fliortening 

of  the  mtrfcles  when  they 
contract. 

402.  Other  things  tvhich  relate  to 

tJie  vis  infita. 


403.  The  nervous  power  of  the 

mufcle. 

404.  In  what  the  nervous  power 

and  vis  infita  differ. 

405.  The  phenomena  in  the  motion 

of  the  mufcles  arifing  from 
the  nervous  power  and  vis 
infita. 

406.  What  the  arteries  contribute 

to  the  motion  of  the  mufcles. 

407.  A refutation  of  the  manner  in 

which  the  nerves  are  faid  to 
move  the  mufcles. 

408.  The  nervous  fluid  feems  to 

perform  the  oflice  of  a ftnn- 
uius  ; and  its  moving  caufe 
is  not  the  foul,  but  a law  de- 
rivc*d  from  the  Creator. 

409.  What  things  fliow  that  in  the 

motion  arifing  from  the  vis 
Infita,  the  foul  does  not  in- 
terfere. 

410.  The  difference  between  the 

mufcles  obeying  the  will, 
and  thofe  which  are  govern- 
ed bv  the  vis  infita. 

411.  The  magnitude  and  lofs  of  the 

powers  which  the  mufcles 
exert  in  their  contradhons. 

41 2.  The  reafon  of  thefc  lofl'cs. 

413.  The  effedts  of  antagonifls,  as 

they  are  called,  in  mufcular 
motion. 

414.  Other  helps  to  this  motion. 

416.  The  co-operation  of  the  muf- 

cles. 

417.  The  effedis  produced  by  the 

adlion  of  the  mufcles. 

418.  The  relaxation  of  a mufcle  at 

refl. 

What  becomes  of  the  fpirit 
fent  from  the  brain. 


CHAP. 


INDEX. 


4S3 


CHAP.  XII, 
TOUCH. 


419.  Senfation. 

Account  of  the  arrangement. 
440.  Touch  in  general. 

431.  Touch  in  another  and  more 
proper  fenfe. 

433.  The  true  Ikin. 

433.  The  granulation  and  papillse 

of  the  fkin. 

434.  The  epidermis. 

435.  The  rete  Malpighianum. 

436.  Of  what  the  network  and  epi- 

dermis confift. 

437.  The  glands  of  the  Ikin. 

There  is  another  fource  of  oily 

liquor  ; what  it  is. 

438.  The  hairs. 

439.  The  nails. 

430.  The  fubcutaneous  cellular  tex- 

ture in  very  few  places  is 
without  fat. 

What  purpofe  it  ferves  after 
it  has  received  the  fat. 

The  Ikin  and  Malpighian  mu- 
cus, and  epidermis,  where 
they  feem  perforated,  are 
drawn  inwards,  and  degen- 
erate. 

431.  The  mode  of  touch,  and  the 

qualities  whieh  are  known 
by  it. 

433.  The  Malpighian  mucus,  hairs 
and  nails,  what  purpofe? 
they  ferve. 


433.  Thevapour  perfpiring  through 

infinite  little  arteries  of  the 
Ikin. 

434.  The  ways  of  demonftrating 

this  exhalation. 

435.  Sweat. 

436.  The  elements  of  perfpiration. 
Water. 

The  odours  of  aliments. 

The  eledtric  matter. 

437.  Another  element  of  perfpira- 

tion, fomething'  volatile,  of 
an  alkaline  nature. 

438.  The  quantity  of  perfpiring  li- 

quid, 

439.  The  indication  from  the  quan- 

tity of  perfpiring  liquid. 
What  things  augment  or  di- 
minifli  it,  and  what  follows 
from  thence. 

440.  How  fweat  benefits  or  hurts 

the  body. 

441.  The  ufe  of  perfpiration.' 

443.  Inhalation,  by  what  arguments 

it  is  proved. 

443.  How  it  is  proved  that  both  the 
exhaling  and  inhaling  veflels 
may  be  contradfed  and  re- 
laxed by  the  power  of  the 
nerves. 


CHAP.  XIII. 
TASTE. 


444.  Tafte  Is  chiefly  exercifed  by 

the  tongue. 

445.  The  tongue  in  general. 

Firfl  Idnd  of  its  papills. 

446.  The  fungiform  papillce. 

The  conical  ones. 

Others  which  intervene. 

447.  The  nerves  of  the  tongue. 

448.  The  arterious  and  nervous  vil- 

li which  run  between  tliem. 

449.  The  covering  of  the  tongue. 


430.  The  mufcles  of  the  tongue, 
451.  The  veffcls  of  the  tongue. 

453.  The  manner  of  exerciling  the 

tafle. 

Flavours,  and  their  caufe. 

453-  What  things  contribute  to  the 
perception  of  taftes. 

454.  The  fpirits  are  refumed  either 

into  the  papilla;  or  the  ab 
forking  villi  of  the  tongue, 
45 j.  The  ufe  of  the  fenfe  of  tafte. 

CHAP, 


484. 


INDEX. 


CHAP.  XIV. 
SMELL. 


456.  The  life  of  firell. 

457.  Smell  is  exercifed  by  the  help 

of  the  membrane  of  the  nof- 
trils. 

The  nerves  of  that  membrane. 

458.  The  arteries  and  veins  of  the 

membrane  of  the  noftrils. 

459.  Whaf  the  noftrils  are. 

'i'he  feptum  of  the  noftrils. 

460.  The  uppermoft,  middle,  and 

lowcft  ofta  fpongiofa. 

461.  The  finufes  in  general,  T.vhat 

they  are. 

The  frontal  finufes. 

462.  The  ethmoidal  finufes. 

The  finus  of  the  multiform 
bone. 

463.  The  finus  of  the  maxillary 

bone. 


464.  The  mucus  of  the  noftrils. 

The  finufes  abounding  in  mur 

cus  can  evacuate  it  in  the 
dilFerent  fituations  of  the 
body,  fo  that  feme  of  thtin 
can  alvrays  empty  them- 
felves. 

465.  The  nofe  and  its  mufcles. 

466.  The  m.anner  of  exerciung  the 

fenfe  of  fmell. 

In  what  it  agrees  or  difagrees 
■with  the  fenfe  of  tafte. 

467.  Tlie  ftrength  of  odours. 

The  parts  t'f  the  noftrils  -which 
principally  belong  to  the 
fenfe  of  Imelliug. 


CHAP.  XV. 
HEARING. 


468.  The  reafon  of  the  difference 

between  the  organ  of  hear- 
ing and  that  of  the  other 
fenles. 

469.  The  external  ear  and  its  parts. 

470.  The  glands  and  mufcles  of  the 

ear. 

471.  The  meatus  auditorius. 

472.  The  ftcin  and  cuticle  of  the 

meatus. 

The  glands  for  feparating  its 
wax  ; the  xyax. 

473 — 477.  The  phyfical  properties 
of  the  air. 

474.  Tones. 

475.  The  velocity  of  found. 

476.  Sym.pathetic  trem.ors. 

1 he  ftrength  of  found. 

Echo.' 

.477.  How  found  rebounds  from 
hard  bodic§. 

The  caufe  of  the  inrreafe  and 
diminution  of  founds. 

478.  The  coUedfion  of  founds  in  the 
meatus  auditorius; 


479.  The  membrane  of  the  tt-mpa- 

num. 

The  founds  ftrike  upon  it  after 
their  iiltim-ate  refledfion  in 
the  meatus  auditorius. 

480.  The  tvmpanum. 

481.  The  four  little  bones  of  hear- 

ing are  placed  in  the  tym- 
panum. 

The  malleu.s. 

482.  The  mufcles  of  the  malleus. 
The  effedfs  of  the  rupture  of 

the  membrane  of  the  tpnpa- 
num. 

483.  The  incus. 

• 484.  The  Rapes  and  its  mufcle. 

483.  The  little  round  bone. 

486.  Various  canals  go  out  of  the 
cavity  of  the  ttTnpanum. 
The  appendix  to  the  tympa^ 
num,  of  the  figure  of  a gno- 
mon. 

The  cells  above  the  mamillary 
procefs,  and  in  the  procels 
itftlf. 


487-  The 


INDEX.  485 


487.  The  tube. 

488.  Two  other  pafTages  lead  from 

the  tympanum  into  the  lab- 
yrinth. 

The  oval  fencflra. 

The  velKbulum. 

489.  The  femicircular  canals. 

490.  The  round  feneftra. 

The  cochlea. 

491.  The  velTels  of  the  organ  of 
, hearing. 

49Z.  The  nerves  belonging  to  this 
organ  remain  to  be  defcrib- 
ed.  ■ 


The  feventh  pair  of  nerves, 
and  its  hard  portion. 

The  nerves  of  the  external  car. 
493.  The  foft  branch  of  the  feventh 
pair  of  nerves. 

494 — 5.  Various  remarks  concern- 
ing the  feat  of  hearing. 

496.  What  things  are"  known  with 

more  certainty  concerning 
this  matter. 

497.  The  dlllindion  and  agreeable? 

nefs  of  founds. 


CHAP.  XYL 
SIGHT. 


498.  The  difference  between  light 

and  hearing. 

The  organ  of  light  is  neceffa- 
rily  compounded- 

499.  The  eyebrow, 
joo.  The  eyelids. 

The  conjundtiya. 

The  nerves  and  arteries  of  the 
palpebrse. 

501.  The  tarfas. 

The  levator  mufcle  of  the  up- 
per eyelid. 

The  orbicularis  palpebrarum. 
501.  The  eyelallies. 

503.  The  Meibomian  febaceous 

glands. 

504.  The  tears  and  their  fources. 

505.  The  dudt  of  the  lachrymal 

gland. 

The  effedts  of  the  contradlion 
of  the  orbicular  mufcle. 

506.  What  becomes  of  the  tears. 
The  caruncula  lachrymalis. 
The  third  palpebra. 

The  pundtum  lachrymale. 

507.  The  dudlus  lachrymalis. 

The  lachrymal  fac. 

The  nafal  dudl. 

508.  The  figure  of  the  eye. 

The  orbit. 

The  furrounding  fat. 

509.  The  optic  nerve. 

Its  courfe. 

510.  What  becomes  of  it,  after  it 

touches  the  eye. 

The  fclerotica. 


The  cornea. 

513.  The  choroides. 

The  Ruyfchian  lamina, 

The  ciliary  circle. 

The  pupil. 

The  iris. 

The  uvea. 

The  membrane  lliutting  the 
pupil  in  the  foetus. 

513.  The  motion  of  the  iris. 

514.  The  ciliary  ligaments. 

515.  The  retina. 

516.  The  humours  of  the  eye. 

The  vitreous  humour. 

517.  The  cryltalline  lens. 

318.  The  aqueous  humour. 

The  chambers  of  the  eye. 

519.  The  llraight  mufcles  of  the 

eye. 

520.  The  oblique  mufcles  of  the 

eye. 

521.  522.  The  nerves  of  the  eye. 

321.  The  ophthalmic  branch  of  the 

fifth  pair. 

322.  The  branches  of  the  third 

pair. 

323.  The  motion  of  the  ciliary  pro-- 

ceffes. 

324 — 527.  The  arteries  of  the  eye- 

328.  The  veins  of  the  eye. 

329.  Light  in  general. 

330.  Light  confills  of  rays  of  differ- 

ent colours. 

531.  Whence  the  colours  proper  to 
every  body  arife. 

Opaque  bodies,  what. 

532.  What 


486  INDEX. 


53  j.  Wliat  refradklon  is,  and  its 
laws. 

S3  3'  When  rays  fall  on  a convex 
fpheric  body,  which  of  them 
are  refradcd,  and  which  re- 
fieifted. 

The  focus  of  refracted  rays. 

534.  What  rays  falling  upon  the 

cornea  are  refledted,  or  being 
refracted  are  fufFocated,  or 
reach  the  lens. 

535.  How  the  rays  are  refradted  in 

their  pafTage  through  the 
cornea  and  aqueous  humour. 

536.  How  they  are  refradted  by  the 

cryftalline  humour. 

538.  How  they  are  refracted  bje  the 

vitreous  humour,  and  are  at 
laft  colledtcd  upon  the  reti- 
na. 

539.  Whether  objedts  are  rather 

painted  on  the  choroides. 

540.  541.  How  the  eye  is  thought 

to  accommodate  itfelf  to  the 
variotts  diftances  of  objedts. 

542.  But  nothing  of  this  kiud  hap- 
pens. 


543.  Myopia. 

544.  The  cure  for  this  difordcr. 

545.  Prefbyopia. 

546.  The  remedy  for  prefbyopia. 

547.  A medium  between  fliort  and 

long  fightednefs  is  l>efl. 

548.  In  what  manner  we  judge  o£ 

• the  magnitude  of  objeefe. 

549.  The  force  of  the  light,  and  its 

effects. 

550.  How  the  place  of  an  objedl  is 

ellimated. 

551.  Diflance. 

552.  How  we  perceive  objjedb  to  be 

gibbous. 

553.  In  what  manner  we  judge  of 

the  fituation  of  the  parts  of 
objedts. 

554.  The  images  of  objedts  remain 

for  a little  time,  even  after 
the  objedts  themfelves  arc 
removed. 

555.  Various  queltions  concerning 

vihon. 


CHAP.  XVII. 


INTERNAL  SENSES. 


556.  Senfation  takes  place  when  a 

new  perception  arifes  in  the 
mind  by  the  pcrcullion  of  a 
nerve. 

The  perception  is  not  the  im-. 
age  of  the  objedt  affecting 
tlie  nerve. 

The  connedtion  between  the 
changes  in  the  nerves  and 
the  perceptions  produced  by 
them  in  the  mind,  is  arbi- 
trary. 

Why,  notwithflanding  this, 
what  we  perceive  of  this 
world  is  not  falfe. 

557.  What  things  are  combined 

wlien  we  perceive. 

558.  The  changes  produced  by  ob- 

jedts  in  the  nerves  remain  a 
long  time  in  their  origin. 
The  prefervation  and  order  of 
thefe  ideas. 

559.  Imagination,  what  it  is, 

■/ 


560.  Memory. 

561.  At  what  times  of  life  the  mem- 

ory and  imagination  flour- 
ith,  and  when  they  decay. 

562.  Thought ; attention. 

Judgment ; genius. 

The  fources  of  error. 

563.  Soundnefs  of  judgment,  on 

what  it  depends,  and  by 
what  it  is  impaired. 

564.  What  ideas  molUy  affedl:  the 

will. 

565.  The  affedtious  of  the  mind. 
Effects  of  the  affedtious  of  the 

mind. 

566.  The  caufes  of  tltcfe  effedts. 

567.  The  pathons  of  the  mind  are 

faithfully  expreffed  in  the 
countenance. 

Phyhognomy,  whence  It  arifes, 

568.  Cec-.fent  of  parts,  whence  it 

arifes. 


569.  The 


INDEX. 


^69.  The  nature  of  the  foul  is  dif- 
ferent from  the  body. 

570.  The  foul,  however,  is  mod  in- 

timately connected  with  the 
body. 

571.  We  have  no  reafon  to  be 

adiamed  of  our  ignorance 
of  the  manner  of  this  con- 
nedlion. 

572.  By  what  arguments  thofc  are 

chieflyperfoaded  who  derive 
the  origin  of  all  the  motions 
and  actions  ia  the  body 
from  the  foul. 

S73j  576-  What  circumftances  do 
not  permit  us  yet  to  adopt 
that  opinion. 

577.  Watching. 

Sleep. 

578.  Dreams. 

With  thefe,  fome  voluntary 
motions  are  fometimes  coi^- 
joined. 


4S7 

579,  What  acShions  continue  to  be 
carried  on  during  fleep. 

58a  Plow  the  mechanical  caufe  ef 
deep  is  to  be  difcovered. 
The  phenomena  of  watching 
and  of  fleep. 

581,  584.  What  things  contribute 
towards  fleep,  or  produce 
it. 

585.  The  proximate  caufe  of  fleep. 

586,  587.  This  is  confirmed  by  the 

caufes  of  watching,  and  what 
thefe  caufes  are. 

588.  The  feat  of  fleep  is  not  in  the 

’ . ventricles  of  the  brain. 

Why  the  vital  adlions  go  on 
in  the  time  of  fleep. 

589.  The  effedts  of  fleep. 

590.  Various  queftions  concerning 

fleep. 


CHAP.  XVIII. 


MANDUCATION,  SALIVA,  and  DEGLUTITION.- 


591.  Moll:  kinds  of  food  need  man- 

ducation. 

592.  Therefore  mod  animals  are 

furniflied  with  teeth. 

Their  drudlure  in  general. 

593.  In  man,  on  account  of  their 

diverlity  of  food,  there  are 
different  kinds  of  teeth. 

The  incifors. 

594.  The  eanine  teeth. 

595.  The  grinders. 

596.  The  teeth  are  fixed  in  the  jaw- 

bones. 

The  various  motions  and  ar- 
ticulations of  the  lower  jaw. 

597.  The  levators  of  the  jaw. 

The  pterygoideus  externHs. 

598.  Hew  the  jaw  is  deprelfed. 

599.  The  powers  of  the  levator 

mufcles. 

The  mufcles  producing  a late- 
ral and  circular  motion  of 
the  jaw. 

600.  The  cheeks. 

The  lips. 

The  mouth. 

The  fituation  and  mobility  of 
the  tongue  in  the  mouth. 


^01.  The  liquor  poured  upon  the 
aliments  during  madication. 
Its  fources. 

The  dudtus  incilivus  is  imper- 
vious. 

602.  The  fallva. 

603.  The  parotid  gland. 

The  gland  called  the  accefibfy 
gland. 

604.  The  maxillary  gland. 

The  fublingual  gland. 

60J.  Thefe  being  comprefled  in 
madication,  pour  out  their 
liquor. 

Appetite  alone  alfo  produces 
the  fame  effedts  with  com- 
preffion. 

606.  The  aliments  are  triturated 

with  faliva  and  air  into  a 
pade. 

They  are  rendered  fapid. 

The  volatile  parts  are  reforbed. 

607.  The  motions  of  the  tongue  for 

revolving  the  aliment  with- 
in the  cavity  of  the  mouth. 

608.  The  tongue  is  diredted  by  the 

os  hyoides. 

The 


488 


INDEX. 


TRe  mufclcs  deprefEng  the  os 
hyoides. 

609.  The  miifcles  raihng  the  os  hy- 

oides. 

610.  The  mufcles  of  the  cheeks  and 

lips. 

611.  The  aliment  being  che^ved  is 

applied  to  the  tongue,  and 
carried  towards  the  fauces. 
61Z.  How  the  food  is  carried  from 
the  mouth  into  the  fauces. 
How  the'accefs  into  the  larynx 
is  doled. 

613.  The  pharynx. 

614.  The  mufcles  dilating  the 

pharynx. 

€15.  How  food  is  prevented  from 
falling  into  the  larynx. 

The  velum  of  the  palate. 

The  uvula. 

616.  How  the  return  of  the  aliment 
into  the  mouth  is  prevented. 
How  tl>e  epiglottis  and  uvula 


are  erected  after  thev  hav^ 
been  deprefl'ed. 

617.  The  powers  which  prefs  the 

aliments  downwards  through 
the  pharynx. 

The  action  of  the  arytenoid 
mufcles. 

618.  The  mucus  of  the  pharvnx, 

and  its  various  fources. 

619.  The  tonhls. 

The  mucus  of  them  Is  very 
vifcid. 

The  neighbotiring  fiarts  arc 
full  of  mucous  organs. 

The  mucus  of  the  cefophagus 
is  more  fluid. 

The  veflcls  of  the  tonfils, 
pharynx,  and  ccfophagus. 
619.*  The  oefophagus. 

6zo.  The  paffage  of  the  aliment 
through  the  oefophagus. 

6zi.  The  conftriction  of  the  upper 
orifice  of  the  ilomach. 


CHAP.  IX. 

The  action  of  the  STOMACH  on  the  ALIMENTS. 


fzz.  Tlie  fituation,  figure,  and  &ze 
of  the  Ilomach. 

6Z3.  The  vilcera  in  the  neighbour- 
hood of  tlie  ftom.ach. 

6z4.  The  external  membrane  of  the 
flomach. 

The  firft  cellular  coat. 

6zy.  The  mufcular  coat  of  the  fto- 
mach. 

The  ligaments  of  the  pydonis. 

6z6.  The  fecond  cellular  coat. 

The  nervous  coat  of  the  fto- 
mach. 

The  third  cellular  coat. 

The  villous  coat. 

The  valve  of  the  pylorus. 

The  pores  of  the  villous  coat. 

6zy.  The  arteries  of  the  flomach. 

628.  The  diftribution  of  the  arteries 
through  the  coats  of  the  flo- 
mach. 

619.  The  veins  of  the  flomach. 

630.  The  nerves  of  the  flomach. 

631.  The  lymphatic  veflcls  of  the 

flomach. 

632.  The  inorganic  pores. 

623.  The  mucus  anointing  the  vil- 
lous membrane. 


The  limpid  humour  which  the 
arteries  diflii. 

634.  The  prefl'ure  of  the  diaphratm 

and  mufcles  of  the  abdomen 
on  the  itcmach. 

635.  The  necefiity  of  meat  and 

drink. 

636.  The  phenomena  of  hanger. 

63  7.  New  chyle,  its  ufes. 

638.  The  caufe  of  hunger. 

639.  The  feat  of  third. 

How  it  is  excited. 

How  quenched. 

640.  The  pleafure  of  taking  food. 

641.  Our  diet  ought  to  conllft  of 

two  kinds  of  t.li.mentE  blen- 
ded together. 

642.  Why  flefti  is  required. 

643.  Why  vegetables. 

644.  Drink. 

645.  Condiments. 

646.  Preparations  of  aliments. 

647.  The  meafure  of  footl. 

648.  The  changes  which  happen  to 

the  food  in  the  flomach. 

649.  What  hinders  the  food  from 

degenerating  into  complete 
acidity  in  the  flomach. 

There 


INDEX. 


't'liere  Is  no  kind  of  ferment 
here. 

650.  The  Deriftaltic  motion  of  the 

llomach  propelling  the  ali- 
ment into  the  inteftincs. 

651.  The  more  powerful  force  of 

the  diapliragm  and  abdomi- 
nal mufcles. 


489 

In  what  order  and  time  the 
aliments  go  out  of  the  fto- 
niach. 

654.  A certain  portion  of  drink  is 
abforbed  in  the  llomach  In- 
to the  veins. 

653.  Vomiting. 

654.  Order  of  arrangement. 


CHAP.  XX. 

The  omentum. 


655.  The  peritoneum  and  its  ex- 
tent. 

6j6.  The  cellular  texture  placed 
round  the  peritoneum  is  con- 
tinued into  the  capfules. 

Its  connexion  with  other  parts. 

657.  The  produdlions  and  ligaments 

of  the  peritonseum. 

By  the  feparated  lamihse  of 
the  peritoneum  the  vifcera 
ate  furrounded,  and  kept 
firm  and  defended  in  motions 
and  concuflions  of  the  body. 

658,  659.  The  mefocolon. 

660.  The  mefocolon  and  mefentery 
are  hollow. 

The  (lender  purfes  of  the  me- 
focolon. 

66  r.  The  mefentery. 

662.  What  things  are  found  in  all 

parts  of  the  mefentery  and 
mefocolon. 

663.  M.anv  parts  are  comprehended 

under  the  name  of  omen- 
tum. 

Their  nature  in  general. 

The  membrane  from  the  ex- 
ternal membrane  of  the  co- 
lon inferring  itfelf  into  the 
Sflure  of  the  liver. 


The  natural  orifice,  and  com- 
mon porta  of  the  omentum. 

664.  The  lefler  hepatico-gallric  o- 

mentum. 

665.  The  anterior  lamina  of  the 

greater  gallro-colic  omen- 
tum. 

666.  Its  poflerlor  lamina. 

667.  The  omentum  colicum. 

668.  It  is  common  both  to  the  o- 

mentum  and  mefentery  to 
. accumulate  fat. 

How  it  Is  proved  that  this  fat 
is  received  into  the  veins. 

669.  The  arteries  of  the  omenta. 

676.  The  nerves  of  the  omenta. 

671.  The  arteries  of  the  mefentery 

and  mefocolon. 

672.  The  veins  of  the  omentum  and 

mefentery. 

The  lymphatic  veffels  of  the 
omentum. 

673.  Other  ufes  of  the  omentum. 

674.  The  ufe  of  the  mefentery. 

675.  The  nature  of  the  water  ab- 

forbed by  the  veins  of  the 
mefentery,  and  what  it  con- 
tributes towards  the  bile. 


CHAP.  XXI. 

The  spleen. 


676.  The  fubflance  of  the  fpleen. 
Its  figure. 

Connedlion. 

Its  fituation,  bulk,  and  num- 
ber. 

I i 


677.  The  arteries  and  veins  of  the 

fpleen. 

678.  The  lymphatic  velTels  of  the 

fpleen. 

679.  Its  nerves. 


6 So.  Its 


INDEX. 


49^ 

680.  Its  internal  flru^ure.  Its  nature. 

Its  furrounding  ineDibrane.  682 — 3.  The  ufe  of  the  fpleen. 

681.  The  fpleen  contains  a great  684.  ConjeiTurcs  ccuceruing  it. 

deal  of  blood. 


CHAP.  XXII. 

The  pancreas. 


685.  The  pancreatic  juice. 

686.  The  fituation  and  figure  of  the 

pancreas. 

Its  Ilrudfure. 

Its  ve'fcls. 

Ils  nerves. 

687.  The  pancreatic  duiT. 

683.  The  quantity  of  pancreatic 
juice. 


The  powers  by  which  it  is  ex- 
pelled. 

1 he  univerfality  of  the  pan- 
creas is  an  argument  of  its 
utility. 

Whence  the  efFervefcence  with 
the  bile  arifes. 

688.*  The  utility  of  the  pancreatic 
juice. 


CHAP.  XXIII. 

The  liver,  GALL  BLADDER,  and  BILE. 


6S9.  The  bulk  of  the  liver. 

The  fituation  of  the  liver  in 
refpedf  to  the  diaphragm. 
The  ligaments  from  it. 

Other  ligaments. 

How  it  can  be  moved. 

Its  common  membrane. 

690.  How  the  liver  is  fituated  with 

refpecl  to  the  colon,  kid- 
neys, duodenum,  flomach, 
and  pancreas. 

691.  The  ihape  of  the  liver. 

692.  The  furrows  of  the  liver. 

Its  lobes. 

693.  The  arteries  of  the  liver. 

694.  The  umbilical  vein. 

The  ductus  venofus. 

695.  The  large  trunks  of  the  vena 

portarum. 

696.  The  capfule  of  the  vena  por- 

tarum. 

The  divifions  of  its  branches. 
Thefe  are  perpetually  accom- 
panied by  branches  of  the 
hepatic  artery. 

The  proportion  of  the  branch- 
es of  the  vena  portarum  to 
the  trunks. 

697.  The  branches  of  the  cava. 

Theproportio.nof  its  branch- 


es to  thofe  of  the  vena  por- 
tarum. 

The  trunk  of  the  vena  cava. 
The  fmaller  veins  creeping 
over  the  furface  of  the  liver. 

698.  The  palTage  of  the  blood 

through  the  vena  portarum. 

699.  The  nerves  of  the  liver. 

700.  The  hmphatic  velTcls  of  the 

liver. 

701 — 3.  The  internal  Ilrmflure  of 
the  liver. 

704.  How  it  happens  that  the  bile 
is  not  fecreted  from  the  hep- 
atic artery,  but  from  the  Ve- 
na portarum. 

703.  How  the  fecreted  bile  is  fent 
into  the  biliary  duels  and 
through  them. 

706.  The  ftructure  of  the  bUiary 

duct 

Its  irritability  and  fenfibllity. 

707.  The  dudlus  choledochus. 

708.  The  dudVus  cvllicus. 

The  gall  bladder. 

Its  fituation. 

709.  The  fhape  of  the  gall  bladder. 
The  wrinkles  of  the  dudlus 

cylHcus. 

710.  The 


INDEX.  49! 


yio.  Tliecoatsandmuciferouspores 
of  the  gall  bladder. 

The  exhalation  of  the  arteries 
into  the  gal!  bladder. 

The  bile  exudes  through  in- 
organic pores. 

Ill,  In  man,  no  dudts  come  from 
the  liver  into  the  gall  blad- 
der. 

711.’*'  The  bile  flows  into  the  in- 
teftine  both  from  the  liver 
and  from  the  gaU  bladder. 

All  the  bile  is  not  firll  con- 
veyed to  the  gall  bladder. 

The  quantity  of  bile. 

How  often  the  bile  flows  into 
the  bladder. 

The  gall  bladder  does  not  fe- 
Crete  its  proper  bile. 


713.  The  return  of  bile  into  the 
blood  is  morbid. 

713.  The  change  which  the  bile  un- 

deigoes  in  the  cyftis. 

It  is  directed  into  the  gall 
bladder,  when  there  is  no 
ufe  for  it  in  the  intellines. 

714.  The  powers  which  exprefs  the 

bile  from  the  gall  bladder. 

715.  The  qualities,  elements,  and 

offices  of  the  bile. 

716.  Whither  the  bile  goes. 

It  fometimes  comes  into  the 
Ilomach. 

The  bile  of  the  foetus. 

Its  coagulation  and  ufes. 

717.  The  proper  ufe  of  the  hver  in 

the  fetus. 


C H A P.  XXIV. 

The  small  INTESTINES. 


718.  The  fmaU  intellines  in  general. 
Their  divifion. 

719.  The  duodenum. 

In  it  chiefly  tlte  bile  and  pan- 
creatic juice  are  mixed  with 
the  aliments. 

730.  The  fituation  of  the  reft  of  the 

frnall  intellines  in  general. 

731,  37.  The  ftrudture  of  the  fmaU 

intellines. 

731.  The  external  coat. 

The  firll  cellular  coat. 

733.  The  mufcular  coat. 

733.  The  fecond  cellulai  coat. 

The  nervous  coat. 

The  third  cellular  coat. 

The  villous  coat. 

Its  folds. 

734.  The  villi  of  the  intellines. 

735.  The  veficles  of  the  villi. 

736.  The  larger  pores  of  the  villous 

coat  leading  to  the  mucous 
glands. 

737.  The  leflcr  pores  Ilkewife  de- 

politing  mucus. 


738,  730.  The  arteries  of  the  fmall 
intellines. 

730.  The  arteries  of  the  duodenum. 

731.  The  veins  .of  the  fmall  intef- 

tines. 

How  it  is  proved  that  thefe 
abforb  a thin  humour  from 
the  intellines. 

733.  The  nerves  of  the  fmall  intef- 
tines. 

733.  The  liquid  flowing  from  the 
arteries  into  the  cavity  of 
the  inl^ftiues. 

Its  quantity. 

The  ides  of  the  mucus  of  the 
fmall  intellines. 

734 — 5-  The  pcriftaltic  motion. 

736.  The  changes  which  the  food 

undergoes  in  the  fmall  in- 
tellines. 

737.  The  office  of  the  fmall  latef- 

tines  in  general. 

738.  The  principal  caufes  which 

chaiige  the  aliments  in  the 
fmall  intellines. 


CHAP. 


INDEX. 


4!J2 


CHAP.  XXV. 


The  large  intestines. 


739.  The  remains  of  the  food  after 

the  chyle  is  extraiSed. 

740.  How  the  ileum  applies  itfelf 

to  the  colon. 

The  valve  of  the  colon. 

741.  The  blind  extremity  of  the  co- 

lon. 

The  appendix. 

How  the  change  from  the 
flruefture  of  the  ca;cum  in 
the  foetus  to  that  of  the  adult 
takes  place. 

The  fetor  of  the  inteflines  be- 
gins chiefly  there. 

74Z.  The  fituation  and  conneclions 
of  the  colon. 

743.  The  flriidture  of  the  colon  in 

general. 

Its  ligaments. 

744.  The  cells  of  the  colon. 

Ike  wrinkles,  follicles,  and 
pores  of  its  villous  mem- 
brane. 

745.  The  vefl’els  of  the  large  intef- 

tine. 

746.  The  diviiion  of  the  veffels  to 

the  large  inteflines. 

The  exhalation  and  reforption 
from  ihefc. 

The  hemorrhoids. 

747.  The  lymphatic  vefTels  of  the 

large  inteflines. 


Chvlc  is  fometimes  cbferved 
in  thefe. 

748.  The  nerves  of  the  large  intef- 

tincs. 

749.  The  faeces  of  the  inteflinum 

colon. 

The  perifkaltic  and  antiperif- 
taltic  motion  of  the  colon. 
Flatus. 

750.  How  the  ileum  is  Unit. 

The  paffage  of  the  fatces  thro’ 
the  colon. 

751.  The  fituation  and  courfe  of 

the  rectum. 

752.  The  external  and  mufcular 

coat  of  the  reelum. 

The  internal  Iphincler  of  the 
anus. 

753.  The  villous  coat  of  the  reiSlum. 
Its  folds,  and  mucous  glands. 

* The  febaceous  glands  of  the 
anus. 

754.  The  external  fphimTtcr  of  the 

anus,  and  its  aclion. 

ITo-yv-  the  anus  is  naturally  clo- 
fed. 

753.  The  levator  mufclcs  of  the 
anus. 

756.  The  excretion  of  the  ficet, 

73  7.  I'hc  fxces  themfclves. 


CHAP.  XXV.* 


The  CHYLIFEROUS  VESSELS. 


738.  The  nature  of  the  chyle. 

JJ9.  The  ubforption  of  the  chyle, 
and  its  paffage  through  the 
ladleal  vefTels. 

In  what  aniraals  latfteal  vefTels 
are. found. 

How  they  are  difpofei  in  the 
dixFerent  inteftines. 

760.  The  valves  of  the  laifteals. 

The  caufes  of  the  motion  of 
the  chyle  tlirough  the  coats 
of  the  inteflines. 

776.  The  glands  of  the  mefentery. 


The  chyle  proceeds  from  the 
inteflines  to  thefe  glands. 

762.  What  happens  to  the  chyle  in 

the  glands  of  the  mefenterv. 

763.  The  courfe  of  the  lacTtals  from 

the  mefentcric  glands  to  the 
receptacle  of  the  chyle. 

764.  How  the  paffage  of  the  chyle 

into  the  receptacle  is  de- 
monflrated. 

763 — 6.  1 he  thoracic  duff. 

767.  The  chyle  paffes  to  the  hlocd 
through  the  th^r  cic  du«51. 

768.  The 


INDEX. 


y6S.  The  caufes  of  the  motion  of 
the  chyle  in  general. 

J'69.  The  change  of  the  chyle  dur- 
ing its  circulation  with  the 
blood. 

In  the  inteflines  there  are  not 
lacteal  and  lymphatic  veffels 
of  difl'erent  kinds. 


495 

770.  The  lacteal  veflels  abforb  wa- 
ter when  digeftion  does  not 
go  on. 

The  thoracic  dui5t  brings  bact 
the  lymph  of  the  whole  bp- 
dy. 


CHAP.  XXri. 

P 

The  kidneys,  BLADDER,  and  URINE. 


771.  A part  of  the  water  brought 

into  the  blood  with  the  chyle 
is  ftrained  through  the  kid- 
neys. 

772.  The  liuiation  and  connection 

of  the  kidneys. 

Their  figure. 

External  membrane. 

Their  fat. 

Ligaments. 

773.  The  arteries  of  the  kidney’s. 

774.  The  veins  of  the  kidneys. 

The  quick  pafiage  of  the  blood 

from  the  arteries  into  the 
veins. 

The  veins  of  the  renal  fat. 

77j.  The  lymphatic  veins  of  the 
kidneys. 

776.  The  nerves  of  the  kidney's. 

777.  The  renal  capfule. 

778 — 8a  The  internal  flrudture  of 
the  kidney'. 

778.  The  Itructure  of  the  cortical 

part. 

The  uriniferous  vefTels. 

The  gland,s. 

779.  The  papillx  of  the  kidneys. 

780.  The  infundibula. 

The  pelvis. 

781.  The  lecretion  of  urine. 

The  quantity  of  the  urine. 

782.  The  elements  of  the  urine. 

783.  How  the  ureter  carries  the  u- 

rine  forwards. 

The  ureter  itl'elf. 

784.  How  it  is  proved  that  the  urine 

is  fecreted  in  the  kidneys, 
and  defeends  by  the  ureter 
into  the  bladder. 

7§r.  The  urine  cannot  defeend  by 
other  palTages. 

786.  The  lituation  of  the  urinary 
bladder. 


787.  The  figure  and  magnitude  of 

the  bladder. 

788.  The  lirtt  cellular  coat  of  the 

bladder. 

Itsiongitudinalmufcular  fibres. 

789.  Its  other  mufcular  fibres. 

790.  The  contractile  power  of  the 

bladder. 

791.  The  fecond  cellular  coat  of  the 

bladder. 

The  nervous  coat. 

The  innermoft  coat  of  the 
bladder. 

The  mucus  of  the  bladder,  and 
its  fources. 

79a.  The  veffels  ai>d_nerves  of  the 
bladder. 

The  lymphatic, 

793.  The  bladder  tranfmits  and  ab» 

forbs  water  through  its  ip- 
organic  pores. 

794.  The  urine  flows  through  tki: 

tireter  into  the  bladder. 

It  remains  there. 

The  caufes  retaining  the  urine. 

795.  How  the  urine  is  expelled 

796.  Various  noxious  matters  TC 

thrown  off  by  the  urine- 
The  confequences  of  a reten- 
tion or  fuppreflion  of  urine. 

797.  The  urethra  in  general 

798.  The  parts  receiving  and  eup- 

porting  the  urethra. 

The  various  capacity  and  fig-, 
lire  of  the  urethra. 

799 — S02.  The  muicles  governing 
the  urethra. 

803.  The  pyramidal  mufclc  has  no 

cffeiT  in  drawing  the  blad- 
der downwards. 

804.  The  mucus  of  the  urethra,  and 

its  various  fources. 

80J.  Theffone  in  the  urinary  bladder. 

CILVP. 


*94 


INDEX, 


CHAR  xxvir. 

The  male  GENITALS. 


806.  The  reafon  of  the  lltuation  of 

the  genital  parts. 

807.  The  order  of  the  arrangement. 
The  various  utuations.  of  die 

tefticles. 

808.  The  ferotunu 
The  dartos. 

809.  Hie  cellular  texture  of  the 

ferotnm. 

The  cremafler. 

810.  The  vaginal  coat  of  the  tefticlc. 
1 he  tunica  albuginea. 

8 1 1.  The  figure  and  fituation  of  the 

epididymis. 

812.  The  fpermatic  arterj-. 

The  abdominal  ring. 

The  courfe  of  the  fpermatic 
cord  from  thence  to  tlie  tel- 
ticle. 

The  fmall  arteries  to  the  cov- 
erings of  the  teftlcle. 

813.  The  dilhribution  of  the  fmall 

arteries  tlirough  the  teflicle. 
The  arteries  have  no  anailo- 
mofes  with  th%  fpermatic 
vein. 

The  motion  and  quantity  of 
the  blood  in  the  tefticle. 

8t4.  The  fpermatic  vein. 

815.  The  vefiTels  of  the  external  cov- 

erings of  the  tefticle. 

816.  The  nerves  of  the  tefticle. 

817.  The  lymphatic  veftels  of  the 

tefticle. 

818.  'I'hc  internal  ftruclure  of  the 

tefticle. 

819.  The  ftruclure  of  the  epididy- 

mis, and  the  vafcula  aber- 
rans. 

820.  The  motion  ©f  the  femen. 

821.  The  vas  deferens. 

822.  The  veficula  feminalis. 

823.  The'fcmen. 

824.  The  animalcules  of  the  femen. 

825.  How  thefe  feem  to  be  in  the 

femen. 


826.  Whence  the  femen  proceeds. 

Of  what  humours  it  is  compof- 

ed. 

What  is  generated  in  the  tefti- 
cles  only  is  prolific. 

How  long  the  femen  is  pre- 
ferved  in  the  vcficks. 

827.  A part  of  the  femen  is  abforb- 

ed,  and  its  effcdls. 

How  the  femen  is  retained  in 
the  veficles. 

828.  The  quantitj'  of  femen. 

The  femen  proceeds  from  the 
tefticle  into  the  velicle. 

829.  The  proftate  gland. 

Its  liquor. 

S29.*  The  three  dilatations  of  the 
urethra ; its  various  direc- 
tioiis ; its  coats. 

830.  The  cavernous  body  of  the 

urethra. 

831.  How  it  is  proved  that  the  blood 

is  poured  into  this  body. 

832.  The  cavernous  bodies  of  the 

penis. 

833.  Tlie  teguments  of  the  penis. 
The  prepuce. 

The  odoriferous  g'ands. 

Tiie  fufpr.dory  ligament. 

834.  The  ufc  of  the  penis. 

S35.  T;:e  creclion  of  the  penis. 

Its  exciting  caufes. 

836.  The  arteries  of  the  genital 

parts. 

837.  The  veins  of  the  fame  parts. 
.838.  The  hunphatic  veffcls  of  the 

penis. 

The  nerves  of  the  genital  parts 

839.  The  i iimediate  caufe  of  the 

ercdlion  of  the  penis. 

840.  The  cxpullion  of  die  femen 

into  the  urethra. 

841.  Its  expuhion  from  the  urethra. 
This  adtion  is  verv  violent, 

and  aunoft  convulftve. 


ChL^J’. 


INDEX. 


<95: 


CHAP.  XXVIII. 
The  virgin  WOMB. 


84a.  The  fituatioTi  of  the  uterus  in 
the  pelvis. 

How  the  uterus  is  tied  to  the 
peritoneum. 

' The  broad  ligaments. 

843.  The  body,  neck  and  internal 

mouth  of  the  uterus. 

844.  The  tubes  of  the  uterus. 

845.  The  ovaries. 

846.  The  eggs  in  the  ovaries. 

847.  The  round  ligament  of  the  ute* 

rus. 

848.  The  arteries  of  the  uterus. 

849.  Its  veins. 

850.  The  internal  veflels  of  the  ute- 

rus. 

831.  The  lymphatic  vefTels  of  the 
uterus. 

85a.  The  nerves  of  the  uterus. 

8 33.  The  age  at  which  the  menfes 
begin  to  flow. 

834.  The  phenomena  of  the  men- 
fes. 

The  duration  of  the  flux. 

The  periods  at  which  they  re- 
turn. 

833.  The  menftrual  blood  flows 
from  the  veflels  of  the  ute- 
rus itfelf. 

The  nature  of  the  menflrual 
blood. 

The  uterus  being  obflrudled, 
the  blood  flows  out  through 
the  vagina,  and  through  oth- 
er parts. 

836.  Whether  the  moon,  ferments, 

or  the  venereal  defire,  be  the 
caufes  of  the  menfes. 

837.  The  female  body  in  general. 


The  pelvis  and  its  vefl*els,in  as 
far  as  they  differ  from  the 
fabric  in  the  male. 

How  the  paffage  of  the  blood 
through  the  uterus  is  thence 
afFe<3:ed. 

839.  The  inferior  limbs,  pelvis,  and 
uterus,  of  a female  child 
newly  born. 

How  the  flrudlure  of  thefe  is 
changed  in  the  adult. 

The  effedls  of  thefe  changes. 

860.  Plethora  is  generated  in  both 

fexes  when  the  growth  of 
the  body  ceafes. 

This,  in  males,  goes  off  by  the 
noflxils. 

In  women  it  finds  an  eafier 
paflage  by  the  uterine  vef- 
fels. 

There  are  other  effedls  of  this 
determination  of  the  blood. 

How  the  quantity  of  the  men- 
fes is  increafed  or  diminifli- 
ed. 

861.  The  quantity  of  the  blood  fent 

out. 

The  remiflion  and  return  of 
the  period. 

Why  the  period  is  commonly 
fixed  to  a month. 

Why  the  menfes  ceafe  to  flow 
altogether. 

Why  brute  animals  have  no 
menfes. 

Why  men  want  them. 

86  a.  Why  the  brealls  fwell  at  the 
fame  time. 


CHAP.  XXIX. 

CONCEPTION. 

863.  The  difficulty  of  this  fubject.  How  they  produce  their  young 

The  order  of  treating  it.  "ones. 

864.  The  molt  Ample  animals  of  no  863.  Oviparous  animals  of  a lingle 

fei.  fex. 

866 — 7.  Animals 


49<>  INDEX. 


866 — 7.  Animils  of  two  fexes  exift- 
ing  in  the  fame  individual. 

866.  Whatauimalsimpregnatetherti- 

felves. 

867.  Animals  of  this  kind  which 

mutually  ftand  hi  ^jccd  of 
one  another’s  affiftaiice. 

8'68.  Animals  with  two  fexes  divid- 
ed. 

yC'p.  Confequences  which  follow 
from  what  has  been  faid 
concerning  the  origin  and 
fexes  of  anim-als. 

870.  Caufes  of  the  venereal  defire. 

871.  The  vagina,  and  its  fituation. 

The  hvmen. 

The  carunculas  myrtifoimes. 

872.  The  ftrudture  of  the  vagina. 

873.  The  nymphac. 

The  clitoris. 

Z~4.  The  confiricfor  mufele  of  the 
mouth  of  the  vagina. 

Eys-  Coition. 

What  happens  to  women  dur- 
ing the  time  of  coition. 

876.  The  fources  of  the  muc'bus  li- 
quor ejected. 

The  tubes  are  eredted  in  coi- 
tion, and  applied  to  the  ova- 
lium. 

877 — 8.  What  changes  take  place 
in  the  ovarium  at  that  time. 

The  corpus  luteum. 

878.  How  it  is  proved  that  the  tube 
prefies  out  the  egg,  abforbs 
it,  and  carries  it  to  the  uterus. 

S79.  The  feelings  of  the  future  mo- 
tlier  while  thefe  things  are 
performed. 

How  It  Is  proved  that  concep- 
tion takes  place  in  the  ova- 
rium. 

28o.  Why  the  uterus  Is  thought  to 
be  Unit  after  conception. 

Whence  the  complaints  after 
conception  arife. 

S81.  The  original  femlna  of  the 
new  animal ; whether  they 
are  from  b.ith  parents,  and 
the  mixture  of  femeii  furuifli- 
ed  from  all  parts  of  the  bodv. 

882.  Whether  they  proceed  only 

from  the  male  and  liis  femi- 
nal  animalcules. 

883.  Whether  the  foetus  proceeds 

ratlier  from  the  mother. 

884.  Hypothefes concerning  the  for- 

mation of  the  nesv  animal. 


885.  What  feems  to  he  more  cer- 
tainly known  concerning  this 
matter. 

806.  The  ftate  of  the  embryo  before 
conception. 

How  it  is  changed  by  the  male 
femen. 

887.  Objedtions  derived  from  moles, 

of  no  weight. 

888.  The  change  of  the  egg  when 

brought  into  the  uterus. 

Its  inofculatiou  with  the  uterus. 

889.  The  contents  of  the  egg  at  that 

time. 

The  foetus  during  the  firft  days 
of  conception. 

890.  The  incrcafe  of  the  egg  and  of 

the  foetus  until  the  placenta 
is  completed. 

Defeription  of  tlic  completing 
of  the  placenta. 

891.  The  placenta,  and  its  connec- 

tion with  the  uterus. 

892.  TIic  chorion. 

893.  The  middle  membrane. 

894.  The  amnion. 

893.  The  umbilical  vein,  by  which 
nouriihmctit  is  conveyed  to 
the  fetus-. 

The  cord. 

896.  The  umbilical  arteries. 

Thefe,  with  tlu  ir  veins  and 

cellular  texture  form  the  pla- 
centa. 

The  blood  flows  from  the  pl.i- 
centa  into  the  veina  of  the 
uterus; 

897.  Whether  the  fetus  takes  in 

the  liquor  of  the  amnion  by 
the  mouth,  and  is  nourilhed 
by  it. 

What  is  the  fource  of  this  li- 
quor. 

898.  The  excrements  of  the  foetus. 

899.  Whether  there  i-  .my  allantois 

in  the  human  race. 

They  certainly  have  an  ura- 
chus. 

The  urine  is  perhaps  depofited 
in  the  cellular  texture  of  the 
cord. 

90c.  A compendium  of  the  forma- 
tion of  the  fatus  mufl  be  giv- 
en. 

901.  What  parts  arc  formed  at  the 
very  firlf  beginning  of  the 
fetus. 

902.  The 


INDEX, 


497 


902.  The  proportion  of  the  fluid  to 

the  folid  parts  at  that  time. 

903.  The  acceflbry  nutritious  juices. 
How  the  blood  and  reft  of  the 

humours  are  perfedted. 

904.  How  the  folid  parts  in  general 

are  formed. 

90J.  The  veffels  are  firft  formed. 
How  they  are  produced. 

906.  What  parts  are  at  firft  com- 

pleted and  become  confpicu- 
ous  in  the  primeval  foetus. 
What  are  as  yet  involved  and 
lie  hid. 

907.  The  motion  of  the  heart  is  ap- 

pended to  this  kind  of  em- 
bryo. 

The  heart  at  firft  bears  the 
largeft  proportion  to  the  reft 
of  the  body. 

Its  pulfations  are  very  power- 
ful in  diftending  and  length- 
ening the  veffels. 

908.  What  is  oppofed  to  this  power 

of  the  heart. 

How  the  arteries  are  then  af- 
fetfted. 

909.  The  foetus,  grows  very  quickly. 
The  caufe  of  this  quick  in- 

creafe. 

910.  The  embryo  is  altered  during 

its  growth. 

910 — 14.  By  what  caufes  this  is 
chiefly  produced. 

910.  Expanfion. 

91 1.  Attradfion. 

912.  Preffure. 

913.  The  power  of  derivation. 

Of  revulfion. 

914.  The  change  of  the  humours. 

915.  How  bone  fucceeds  cartilage 

and  epiphyfis. 

916.  How  the  long  bones  are  form- 

ed. 

917.  How  the  flat  bones  are  formed. 

918.  Plow  bone  is  produced  from 

gluten. 

It  is  depofited  from  the  inmoft 
fubftance  of  the  bone,  and 
not  from  the  periofteum. 

919.  The  periofteum. 

920.  The  foetus  during  the  firft  days 

of  pregnancy. 

921.  The  thymus. 

921 — 24.  The  circulation  of  the 


blood  peculiar  to  the  foetus, 
and  the  organs  by  which  it 
is  performed. 

92J.  Whether  the  foetus  breathes  in 
the  womb. 

Whether  it  docs  fo  in  the  va- 
gina. 

926.  The  changes  which  happen  to 

the  uterus  during  pregnancy. 
The  different  fituations  of  the 
foetus. 

927.  The  complaints  attending  preg- 

nancy. 

The  time  of  delivery. 

928.  Parturition, 

929.  The  number  of  foetufes. 
Superfetation. 

930.  The  loofening  of  the  placenta. 
— of  the  umbilicus. 

931.  The  contradtion  of  the  uterus 

after  delivery. 

The  lochia. 

The  fwelling  of  the  breafts. 

944. *  The  milk. 

Sympathy  between  the  breafts 
and  uterus. 

945.  The  breafts. 

Their  veffels. 

Nerves. 

946.  The  ladtiferous  dudls  In  the 

breaft. 

The  nipple  and  its  ladtiferous 
dudts. 

The  areola  of  the  nipple. 

947.  Sudtion. 

The  coloftra. 

Milk  may  be  produced  with- 
out a child. 

The  breafts,  after  the  menfes 
have  ceafed,  become  effete. 
948 — 52.  The  changes  which  hap- 
pen to  the  child  after  birth. 

948.  Refpiration. 

The  deflexion  of  the  courfe  of 
the  blood  from  the  dudlus 
arteriofus. 

949.  The  flmtting  up  of  the  foramen 

ovale. 

9JO.  The  flrutting  up  of  the  umbili- 
cal vein  and  dudtus  venofus. 

951.  The  contradtion  of  the  umbili- 

cal veins,  and  abolition  of 
the  urachus. 

952.  Other  changes. 


K k 


CHAP, 


45S 


INDEX, 


CHAP.  XXX. 

NUTRITION,  GROWTH,  LIFE,  and  DEATH. 


953.  The  growth  of  a child  is  (low- 

er as  it  advances  in  age. 

The  caufes  why  the  growth  is 
continually  lefTened. 

954.  The  heart  grows  lefs  in  pro- 

portion than  any  other  part 
of  the  body. 

And  becomes  lefs  irritable. 

955.  The  end  of  the  inci^fe  of  the 

body. 

93  6.  When  this  is  faid  to  occur. 

957.  Hqw  it  is  proved  that  all  parts, 

even  the  moft  folid,  are 
continually  confuming  and 
changing.^ 

958.  The  caufes  of  the  deftrucUon 

of  the  folid  parts. 

959.  How  the  wade  of  the  folids  is 

repaired. 

960.  How  the  wade  of  the  cellular 

fubdance  and  mod  organic 
parts  is  repaired. 


961.  How  the  free  extremities  of 

parts  are  repaired. 

962.  Fatnefs. 

963.  The  beginnings  of  decay. 

964.  The  progrefs  of  decay. 

965.  The  diminution  of  the  vis  inli- 

ta  and  nervous  power. 

966 — 8.  The  change  of  the  fluids. 

966.  The  decreafe  of  the  fluids. 

967.  The  corruption  of  the  fluids. 

968.  The  increafe  of  the  qu^tity 

of  earth  in  the  fluids. 

969.  Old  age. 

970.  Decrepit  old  age. 

'97X.  iaOngcnrity. 

972.  Death  from  old  age. 

973.  The  figns  of  death. 

974.  The  body  is  dedroyed  by  pu-* 

trefatdion. 

The  foul  furvives  after  death, 
and  goes  to  the  place  appoint- 
ed for  it  by  the  Almighty. 


FINIS. 


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